Method for cleaning passageways using flow of liquid and gas

ABSTRACT

Apparatus and methods are disclosed for cleaning interiors of passageways in endoscopes or other luminal medical devices by flow of liquid and gas therethrough. The liquid flow may include rivulets, droplets or other liquid entities which move on the internal surfaces of the passageways, and may include a three-phase contact interface between liquid and dry solid and gas.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/286,747 that was filed with the United States Patent and TrademarkOffice on Sep. 30, 2008, and issued as U.S. Pat. No. 8,226,774 on Jul.24, 2012. This application is related to U.S. patent application Ser.No. 12/286,749 that was filed with the United States patent andTrademark Office on Sep. 30, 2008, and issued as U.S. Pat. No. 8,114,221on Feb. 14, 2012. The entire disclosures of U.S. application Ser. No.12/286,747 and U.S. application Serial No. 12/286,749 are incorporatedherein by reference.

FIELD OF THE INVENTION

Embodiments of the invention pertain to the cleaning of passageways suchas in medical instruments such as endoscopes.

BACKGROUND OF THE INVENTION

Medical instruments such as endoscopes and other luminal devices, havinglong narrow passageways, generally have to be cleaned between uses.Current cleaning methods for cleaning the interiors of long narrowpassageways include single-phase liquid flow followed by single-phasegas flow, with the single-phase gas flow mostly used for drying. Use ofmixed-phase flow has been disclosed in patent such as U.S. Pat. Nos.6,027,572 and 6,857,436 and 6,454,871 all to Labib, in a flow regimesuch that gas-driven droplets of liquid strike contaminants and dislodgethem. However, in some situations as in flexible endoscopes, there arepressure limitations which make it impossible or unlikely for gas-drivendroplets to form or if formed, their concentration is very low and theirvelocity is too small to attain sufficient momentum to dislodgecontaminants by impact of droplets. A different regime of cleaning hasbeen disclosed in U.S. Pat. No. 4,781,764 to Leenaars, which has usedsurface tension forces at a moving interface between solid and liquidand gas to remove contaminants from an externally-facing surface of aflat plate. Leenaars' contaminants were inorganic, not biologicallyadhered, and the motion needed to effect cleaning was relatively slow.U.S. Pat. No. 5,279,799 to Moser discloses limited use of liquid and gasflow separately in cleaning endoscopes. There is industrial literatureof two-phase liquid and gas flow but usually involving a wall whichremains wet during the two-phase flow. In these respects and also inother respects, there remains room for improvement in both results andease of performing cleaning.

SUMMARY OF THE INVENTION

In an embodiment of the invention, there is provided an apparatuscapable of supplying to an internal passageway a flow of liquid and gassuch that the liquid flowrate and the gas flowrate have a desiredrelationship with each other. The relationship may be appropriate toproduce a desired flow regime such as rivulet droplet flow on theinternal surface in at least some of the passageway. The relationshipmay be specific to a particular inside diameter and length of thepassageway. Embodiments of the invention may be capable of providingliquid flow and gas flow at appropriate parameter values suitable toachieve meandering rivulet flow or fragmenting rivulet flow or both inat least some portions of a length of a passageway. In an embodiment ofthe invention, there may be provided apparatus appropriate to deliver aperimeter-normalized liquid flowrate of between 1 and 5 milliliters perminute per millimeter of perimeter of the passageway.

In an embodiment of the invention, there may be provided a cleaningliquid that creates high advancing contact angle of 50 degrees or higherand receding contact angle of more than 0 degree to allow the formationof the rivulets and of the rivulet droplet flow as described herein. Inembodiments of the invention, there may be provided surfactants andother ingredients in the cleaning liquid such that three phase contactline can be formed during the liquid droplet flow to create detachmentforces for the purpose of cleaning the surface of the passageway.

In an embodiment of the invention, there may be provided apparatuscapable of causing motion of three phase contact interfaces alonginternal surfaces of a passageway suitably to clean the surfaces. Inembodiments of the invention, there may be provided apparatus such thatindividual patches of surface of the internal surface of the passagewayare sometimes wetted by moving liquid entities and in between suchwettings, those same surfaces de-wet or become dry.

In an embodiment of the invention, there may be provided an apparatuscapable of supplying to an internal passageway a flow of liquid and gassuch that the liquid flowrate has a desired variation as a function oftime. The variation as a function of time may be appropriate to producea desired cleaning action.

In an embodiment of the invention, the apparatus may be capable ofsupplying liquid flow and gas flow to a passageway to be cleaned, suchthat the liquid flowrate and the gas flowrate are both substantiallyconstant, and the apparatus may also be capable of supplying liquid flowand gas flow such that at least one of the liquid flowrate and the gasflowrate has a desired variation as a function of time.

Embodiments of the invention may be capable of providing liquidflowrates and gas flowrates to specific passageways or channels suchthat the magnitudes of the flowrates are unique to the specificpassageway or channel or direction of flow. Embodiments of the inventionmay be capable of providing liquid flowrates and gas flowrates tospecific passageways or channels such that the chronologies of theflowrates are unique to the specific passageway or channel or directionof flow.

Embodiments of the invention may be capable of providing a specificoperating condition conducive to cleaning a first specific portion of alength of a passageway, and a second different operating conditionconducive to cleaning a second specific portion of the length of thepassageway.

Embodiments of the invention may be capable of providing liquid flow andgas flow at appropriate parameter values for an appropriate duration oftime so as to achieve a desired Treatment Number.

Embodiments of the invention may be capable of providing time-varyinggas flow such that periods of reduced gas flow in one channel occurduring periods relatively large flow in another channel. In embodimentsof the invention, pulsations of gas flowrate in respective channels maybe coordinated such that periods of reduced gas flow in one channeloccur during periods relatively large flow in another channel.

In an embodiment of the invention, the apparatus may be capable ofperforming rinsing using rivulet droplet flow.

In an embodiment of the invention, there may be provided an apparatuswhich measured flowrate of gas delivered, and sets the liquid flowrateresponsive to the measured gas flowrate.

In embodiments of the invention, liquid and gas flow may be delivered toa cylinder well such that the liquid and gas distribute themselves amongmore than one channel or channel direction in proportions which closelyresemble the proportion delivered to the cylinder well. In embodimentsof the invention, there may be provided an introduction region in whichgas flow and liquid flow have already come together upstream of theactual endoscope channel being cleaned.

In embodiments of the invention, liquid and gas flow for cleaning can bedelivered to cylinder wells in the control handle of an endoscope. Inembodiments of the invention, liquid and gas flow can be deliveredeither to the umbilical end of the endoscope or to cylinder wells in thecontrol handle of the endoscope, and flow in the control handle sectionof the endoscope can be in either direction or any combination ofdirections for various channels. Embodiments of the invention caninclude appropriate valving to accomplish such flow directions. In anembodiment of the invention, there may be provided an apparatus whichfor certain time periods allows the flow of liquid and gas in bothchannel directions from a supply connection, and at other time periodsallows the flow of liquid and gas only in one channel direction from asupply connection.

An embodiment of the invention may be capable of providing liquid andair to clean a passageway, wherein the air has been dehumidified, orheated, or both, with respect to ambient air that has been taken in.

Embodiments of the invention may include connectors for connecting tocylinder wells, such that the connector contains an actuator to directwhich of various channels or channel directions receive flow.Embodiments of the invention include connectors for connecting tocylinder wells, such that dedicated flowpaths connect to specificchannels or channel directions.

An embodiment of the invention comprises an external washing systemincluding an eductor having an air intake so as to direct a flow ofbubble-containing liquid at external surfaces of an endoscope.

Embodiments of the invention may use specific surfactants or types ofsurfactants or combinations of surfactants during cleaning withsimultaneous liquid flow and gas flow such as rivulet droplet flow.

Embodiments of the invention comprise methods involving the use of anyof the described apparatus.

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

Embodiments of the invention are further described in the followingillustrations.

FIG. 1 a is an illustration of velocity profiles in a viscous liquidflow that fills an entire passageway. FIG. 1 b illustrates localvelocities of such a viscous flow in the vicinity of a contaminantparticle attached to the wall. FIG. 1 c illustrates, in connection withviscous forces from a sliding liquid entity, velocity componentsassociated with the sliding liquid entity. FIG. 1 d illustrates thesliding liquid entity encountering a contaminant particle.

FIG. 2 a is an illustration of a sliding liquid entity on a solidsurface, surrounded by gas and thereby creating three-phase contactinterface. FIG. 2 b is a cross-section of FIG. 2 a illustratingdefinitions of contact angles. FIG. 2 c illustrates, in connection withsurface tension forces, a liquid entity approaching a contaminantparticle. FIG. 2 d illustrates, in connection with surface tensionrelated forces, a liquid entity beginning to encounter a contaminantparticle. FIGS. 2 e and 2 f illustrate force diagrams for surfacetension related forces exerted by a liquid entity upon a contaminantparticle.

FIG. 3 a is an illustration of a meandering rivulet on a flat plate,including an illustration of advancing and receding contact angles dueto sideways motion of the rivulet. FIG. 3 b is a reproduction of aphotograph from a journal article illustrating meandering rivulet flowof liquid on an inclined flat plate in stationary gas.

FIG. 4 is an illustration of possible rivulet behavior on an internalsurface of a cylindrical passageway.

FIG. 5 a is a schematic illustration of possible appearance of variousforms of sliding liquid entities in a passageway. FIG. 5 b schematicallyillustrates liquid entities as a function of amount of liquid flowrate.FIG. 5 c schematically illustrates liquid entities as a function ofposition along a passageway.

FIG. 6 a is a collection of actual photographs illustrating fluidconditions at five positions along the length of a passageway. These arefor a liquid flowrate which is considered to be less than optimum toachieve cleaning using moving three-phase contact. FIG. 6 b is a similarcollection of five photographs. These are for a liquid flowrate which isconsidered to be appropriate for achieving cleaning by the describedmechanism. FIG. 6 c is a similar collection of five photographs. Theseare for a liquid flowrate which is considered to be larger than optimumfor achieving cleaning by the described mechanism.

FIG. 7 a is a map of fluid flow conditions as a function of positionalong the length of a passageway, and as a function of liquid flowrate.This is for a passageway having an inside diameter of 0.6 mm. FIG. 7 bis a similar map for a passageway having an inside diameter of 1.8 mm.FIG. 7 c is a similar map for a passageway having an inside diameter of2.8 mm. FIG. 7 d is a similar map for a passageway having an insidediameter of 4.5 mm. FIG. 7 e is a similar map for a passageway having aninside diameter of 6.0 mm.

FIG. 8 is a compilation of information from FIGS. 7 a-e, furtherillustrating optimum liquid flowrate for various passageway insidediameters.

FIGS. 9 a and 9 b are illustrations of where conditions suitable forcleaning do or do not occur under various operating conditions.

FIG. 10 a illustrates on one of the flow maps where cleaning withsteady-state inputs is possible and where cleaning with unsteady inputsmay be desirable. FIGS. 10 b through FIG. 10 e are schematicillustrations of various possible conditions regarding whether an entirecross-section of a passageway is or is not entirely wetted. FIG. 10 bshows a relatively small inside diameter passageway which is naturallyfilled with a meniscus. FIG. 10 c shows a somewhat larger insidediameter passageway which does not support a meniscus across itscross-section. FIG. 10 d shows a relatively large inside diameterpassageway whose cross-section can be filled with liquid on a dynamicbasis. FIG. 10 e shows the same passageway further along during passageof a plug, with the leading surface of the plug becoming irregular.

FIG. 11 is a timeline illustrating sequences of events related tocreating passage of three-phase contact by a transient mechanism whichis not exactly meandering rivulets.

FIG. 12 is a schematic illustration of overall features of a typicalendoscope.

FIG. 13 a is an overall schematic system diagram of an endoscopereprocessing apparatus. FIG. 13 b shows detail around a manifold forperforming cleaning. FIG. 13 c shows detail related to a patency test.FIG. 13 d shows detail related to the basin for cleaning or disinfectingexternal surfaces of an endoscope.

FIG. 14 is a time sequencing showing performance of various steps duringthe cleaning of an endoscope passageway.

FIG. 15 is a time sequencing showing performance of various steps duringthe simultaneous processing of two endoscopes by a single endoscopereprocessing apparatus.

FIG. 16 a illustrates one configuration of valving of the entrances andexits of certain channels in an endoscope. FIG. 16 b illustrates anotherconfiguration of valving of the entrances and exits of certain channelsin an endoscope.

FIG. 17 is an illustration of a feedback control system for maintainingdesired flow conditions.

FIG. 18 a is a block diagram showing a system for supplying twoendoscope channels, with feedback, using two liquid metering pumps. FIG.18 b is a block diagram showing a system for supplying two endoscopechannels, with feedback, using one liquid metering pump and aproportional valve.

FIG. 19 a is a cross-section of an endoscope showing detail about thecylinder wells in the control handle. FIG. 19 b is a cross-sectionalillustration of a fixed-position connector to cylinder well in thecontrol handle of an endoscope, in which one incoming flowpath joins twodirections of one channel in the cylinder well. FIG. 19 c is across-sectional illustration of a fixed-position connector to a cylinderwell in the control handle of an endoscope, in which two incomingflowpaths each join two directions of two channels in the cylinder well.

FIG. 20 a is a cross-sectional illustration of a fixed-positionconnector joining a cylinder well such that the connector has twodedicated incoming flowpaths each supplying a particular direction of achannel. FIG. 20 b is a cross-sectional illustration of a fixed-positionconnector and cylinder well such that the connector has four dedicatedincoming flowpaths, with the four incoming flowpaths supplying twodirections of two channels.

FIG. 21 a, 21 b, 21 c, 21 d are cross-sectional illustrations of aconnector and cylinder well in which the connector is actuated so as tochoose a particular passageway to supply flow to. FIG. 21 a, 21 b, 21 c,21 d each illustrate different positions of the actuator-drivencomponent.

FIG. 22 a is a top view of a basin with eductors and a flow circuit fordirecting flow at external surfaces of an endoscope. FIG. 22 billustrates an eductor which takes in air by virtue of being locatednear the liquid level of the basin. FIG. 22 c illustrates an eductorhaving an air intake tube. FIGS. 22 d, 22 e are illustrations of designsof basins and eductors for cleaning the external surfaces of endoscopes.

FIG. 23 illustrates an experimental set-up for photography.

FIG. 24 is another flow map taken at a different pressure.

FIGS. 25 a and 25 b illustrate data taken using radionuclides.

FIGS. 26 a and 26 b are flow maps with an extra notation.

DETAILED DESCRIPTION OF THE INVENTION

Flow Regimes of Liquid and Gas Flow

Embodiments of the invention may be designed to create certain flowregimes within an internal passageway of an endoscope or other medicalluminal instrument, for purposes of removing contaminants from theinterior of the passageway. One previously-used way of dislodging acontaminant is by impact of a liquid droplet moving at a sufficientlylarge velocity in a stream of gas. However, in some situations it is notpossible to provide sufficient gas velocity to create droplets or tocreate droplets having momentum sufficient to dislodge contaminants.This limitation may occur, for example, in situations where the deviceincluding the passageway is subject to a pressure limitation which isrelatively low, and/or where the passageway is relatively long, such asin certain channels of endoscopes. For example, depending on the designof a particular endoscope and depending on the particular passagewaywithin the endoscope, the maximum pressure which can be inputted intothe passageway may be limited to 18 psig, or 24 psig, or 28 psig. (Oneparticular channel of some endoscopes may have pressure limit of 70psig.) The flow length of the passageway may be as long as severalmeters. These parameters in combination may limit the achievable gasvelocities within the passageway. The presence of debris andcontaminants can also reduce achievable gas velocity within apassageway.

Therefore, an embodiment of the present invention may use other physicalmechanisms to accomplish cleaning. There are at least two possiblephysical mechanisms that can be active in detaching contaminants by themoving three phase contact line and menisci arising from the slidingmotion of rivulets and surface flow entities formed during the rivuletdroplet flow. One mechanism involves viscous shear, and the othermechanism involves surface tension. The three phase contact line mayindicate the interface between solid (surface of passageway), liquid andair, or in other cases contaminant particle surface, liquid and air. Themeniscus may be defined as a two-dimensional interface of a slidingentity moving on the wall of the passageway. In addition to these twomechanisms, it is further believed that still other physico-chemicaleffects may also be active helping to accomplish cleaning as well,especially in the presence of surfactants other components of thecleaning liquid. These mechanisms, for example, can include dissolutionof contaminants or portions of contaminant particles, and desorption byaction of the surfactant.

Viscous Forces on Contaminant Particles

In regard to viscous shear for removing a contaminant particle, it isinstructive to compare viscous shear forces that might be generated by aconventional bulk flow of liquid filling an entire passageway, ascompared to viscous shear that might be generated by a sliding liquidentity having three phase contact line and satisfying the criteria forhigh advancing contact angle and non-zero receding contact angle whenencountering a particle. The comparison is illustrated in FIGS. 1 a, 1b, 1 c and 1 d.

For a conventional bulk laminar flow of liquid flow through apassageway, the velocity profile is parabolic as illustrated in FIG. 1a. The velocity of the liquid is zero at the capillary wall and ismaximum near the center of the capillary. The velocity as a function ofradial position is given by the following equation.V(z)=2U _(o)[1−(R _(t) −z)² /R _(t) ²]  (1)

where V(z) is the velocity of the flow with a distance z from thecapillary wall. U_(o) is one half of the maximum velocity at the centerof the flow, and R_(t) is the radius of the capillary. In this equation,a represents distance measured away from the wall. In the immediatevicinity of the wall, where z/R_(t)<<1, Equation 1 can further besimplified to give the velocity profile near the wall asV(z)=(4z/R _(t))U _(o)  (2)

For determining hydrodynamic force that can be experienced by acontaminant particle attached to the wall, one may consider that arepresents the radius of the contaminant particle. The mostrepresentative quantity to consider is the liquid velocity at theoutermost point of the contaminant particle whose dimension is 2 a.Thus, the liquid velocity at the outer edge of the contaminant particleis (8a/R_(t))U_(o). Thus, for a particle which is small compared to theradius of the capillary, the liquid velocity seen by the point on theparticle farthest from the wall is only a small fraction of the maximumcentral velocity of the flow. This is illustrated in FIG. 1 b.

A different situation presents itself for flow of a sliding liquidentity attached to the passageway wall and having a three phase contactline at its leading edge. It may be considered that the liquid entityadvances with a sliding velocity of U_(sl). It may further be consideredthat the leading edge of the sliding liquid entity appears as a wedge,and the wedge moves with a velocity profile V(z) which is zero at thecapillary wall and approaching 1.5 U_(sl) at the top of the wedge. Thissituation is described by Pierre-Gilles de Gennes, FrancoiseBrochard-Wyart, David Quere, “Capillarity and Wetting Phenomena”,Springer, 2003. FIG. 1 c (FIG. 6.6 in the de Gennes reference)illustrates the velocity profile within a sliding wedge. This situationoccurs at any point on the sliding wedge, whether the point is near thetip of the wedge where the wedge is quite thin or further back from thetip of the wedge where the wedge is thicker. This is illustrated in FIG.1 c.

For purposes of removal of a contaminant particle, the situation ofinterest is when the contaminant particle attached to the wall islocated within the approaching wedge at the distance x from contact linewhen it touches the water air interface. The smaller the particle is,the smaller the distance x. The mean velocity of liquid stream affectingparticle is about 0.75 U_(sl) because the velocity on the top of thewedge is 1.5 U_(sl), and the velocity at the capillary wall is zero.FIG. 1 d demonstrates that the liquid velocity which affects attachedparticles is at least 0.75 U_(sl), no matter how small a particle isbecause for any small particle there is a distance x to contact linewhere it touches both surfaces.

For any given particle, it is possible to compare the cleaningeffectiveness of a sliding liquid entity against the cleaningeffectiveness of bulk liquid flow, by comparing the liquid velocity atthe edge of the particle for a sliding liquid entity, against the liquidvelocity at the edge of the particle for conventional bulk flow. Thisratio isVedge(sliding liquid entity)/Vedge(bulk flow)=(1.5)(U _(sl) /U _(o))(R_(t) /a)  (3)

It can be seen that as the particle size represented by “a” becomessmall, the advantage of a sliding liquid entity increases compared tobulk liquid flow. For example, when comparing with a bulk liquid flowwith a maximum velocity of 200 cm/sec (U_(o)=100 cm/sec) in a tube whichhas a radius of 0.05 cm (R_(t)), the three phase contact line of asliding liquid entity moving with U_(sl)=1 cm/sec can produce a 2 foldincrease in detachment force compared to the detachment force of bulkliquid flow of 1 micron in radius, a 20 fold increase for the particlesof 0.1 micron in radius, and a 200 fold increase for the particles of0.01 micron in radius.

Thus, it is believed that for whatever are practical values of bulk flowmaximum velocity and practical values of liquid entity sliding velocity,a sliding liquid entity can bring its velocity very close to the wall atthe leading edge of an advancing wedge of the sliding liquid entity,whereas bulk flow cannot bring its maximum velocity near the wall. Thus,a sliding liquid entity has an advantage over bulk flow as far asexerting viscous force on small contaminant particles attached to thewall. However, it is not wished to be limited to this explanation.

Surface Tension Forces on Contaminant Particles

The second possible mechanism to achieve cleaning uses a mechanism thatinvolves a moving three-phase interface on the interior surface of thepassageway, i.e., an interface between liquid and gas at a solidsurface. This cleaning mechanism may involve a portion of the surfacebeing wetted by a liquid entity, and an adjacent portion of the surfacebeing dry or nearly dry. As such an interface moves, it can generateforces that may act to dislodge contaminants. FIG. 2 schematicallyillustrates this situation.

It is believed that as a wet-dry interface moves along a solid surface,the wet-dry interface can exert a force on elements of the surfaces suchas contaminants which may be adhered to the surface. This force maycontribute to breaking the adhesion such contaminants have with theunderlying solid surface such as by lifting such contaminants away fromthe underlying solid surface. This may be termed “capillary flotation.”This can involve moving three-phase contact interfaces and menisci. (Theterm “three phase contact interface” may also be expressed in theliterature as “three phase contact line.”) However, it is not wished tobe limited to this explanation or to situations where this is the onlycleaning mechanism taking place. For purposes of this discussion, it isintended that the terms “wet” and “dry” are such as to allow formationof a three-phase contact interface at the interface between the “wet”region and the “dry” region. In addition to including a situation of aclassical perfectly dry surface, the situation is also intended toinclude possible situations where there might be an extremely thin orintermittent liquid film present, but where the overall behaviordisplays characteristics similar to those of a liquid entity moving on aperfectly dry surface. The dry and wet conditions according to thisdescription may also be expressed in terms of the advancing contactangle, receding contact angle and residual thin liquid film remainingafter passage of three phase contact line. The term dry or nearly dryindicates that the thickness of the residual thin liquid film may besmaller than the dimension of the contaminant present on the surface.

FIG. 2 a illustrates a sliding liquid entity on a solid surface. FIG. 2b illustrates definition of advancing and receding contact anglesassociated with the sliding liquid entity.

A mechanism of detachment can be caused by capillary tension forces atthe liquid/air interface when a meniscus forms around a particle (FIGS.2 c, 2 d, 2 e and 2 f). FIG. 2 c depicts a contaminant particle attachedto a wall being approached by the contact line of a sliding droplet.FIG. 2 d shows the moment when the liquid/air interface touches theparticle. FIGS. 2 e and 2 f only represent the vicinity of the particleduring the process when capillary force is induced for two cases, ahydrophilic)(θ_(p)<90°) particle and hydrophobic particle (θ_(p)>90°).According to this mechanism, touching the particle surface by a movingliquid initiates the onset of the capillary force, no matter whether aparticle is hydrophilic or hydrophobic. However, the contact angle ofthe cleaning liquid with the particle plays a significant role in thedetachment by this mechanism. Selection of surfactant mixture of thecleaning composition may be tailored to enhance detachment ofcontaminants by this mechanism.

Detachment of a hydrophilic particle: When the particle is hydrophilic,an aqueous liquid wets the particle surface leading to expanding thecontact area at liquid/particle surface. This is characterized byexpansion of the contact area perimeter Ψ which represents the contactline on the particle surface. The perimeter movement along the particlesurface is accompanied by the deformation of the liquid surface atparticle vicinity which is manifested by formation of a local meniscus(FIG. 2 e). In this case, it is sufficient to take into account thesurface tension of the liquid/air interface, i.e., the force which isdirected along the interface). This force exists at any point of thecontact line and has different directions. Assuming the particle wettingis axi-symmetrical and takes a shape similar to the contact line, we mayintroduce the local cylindrical system of coordinate with axialcoordinate z and radial coordinate r. The radial components of localcapillary forces cancel each other because of axial symmetry. The axialcomponents are the same for any point of the contact line that yieldsthe total axial capillary force. If the axial force is larger than theadhesion force, the capillary force will detach the particle. In thiscase, the contact angle for particle θ_(p) is less, than 90°.

Interaction with a hydrophobic particle: When the particle ishydrophobic)(θ_(p)>90° its wetting is suppressed and its penetrationinto the liquid is small due to a large value of contact angle as shownin FIG. 2 f. As a result, the direction of capillary force is oppositeto the one shown in FIG. 2 e. In this case, the horizontal component(parallel to wall) of the arising capillary force will cause theparticle to roll and consequently detach from the wall.

To describe nature of capillary force, the well-known equation for theattachment of a spherical particle to a rising bubble in flotation canbe used. The capillary force equation for particle attachment toliquid/air interface is provided by Cristina Gomez-Suarez, et al.,Applied and Environmental Microbiology, 67, 2531-2537 (2001), asfollows:F _(ca)=2πaσ sin Ψ sin(θ−Ψ)  (4)where a is the radius of the particle and σ is the liquid surfacetension. The capillary force is proportional to the length of contactline 2πa sin Ψ and to the surface tension. Sin(θ−Ψ) arises at thetransition from vector F_(σ) to its projection F_(σax) as shown in FIGS.2 e and 2 f. Angle Ψ varies during interaction and, in particular, takesvalue corresponding to the maximum of capillary force:F _(ca) ^(max)=2πaσ sin²(θ/2)(π/2<θ<π)  (5)F _(ca) ^(max)=2πaσ sin²[(π−θ)/2](0<θ<π/2)  (6)

Capillary detachment force compared with hydrodynamic detachment forceinduced by a three phase contact line: The hydrodynamic detachment forceF_(h) near sliding three-phase contact line is represented as:F _(h)=4.5πηaU _(sl)  (7)where η is the liquid viscosity, a is the radius of the particle andU_(sl) is the sliding velocity of the droplet or surface flow entity.The ratio of hydrodynamic force to the capillary force can be expressedas follows:F _(h) /F _(ca) ^(max)=(2.25/sin²θ/2)Ca _(sl)  (8)where Ca_(sl)=ηU_(sl)/σ is the capillary number which is very small. Forexample, assuming the sliding velocity U_(sl) is 5 cm/sec, the liquidviscosity η is 1×10⁻² g/cm·sec and the surface tension of the liquid σis 50 g/s²(dynes/cm), the capillary number is about 10⁻³. Consideringthe contact angle, the ratio between hydrodynamic and capillary forcesfor different θ and U_(sl) is included in the following Table.

F_(ca) ^(max)/F_(h) in Equation (8) U_(sl), cm/sec θ 0.5 5 π 4444 444π/2 2222 222 0 4444 444Although in some cases capillary detachment force is clearly higher,there are situations when the hydrodynamic detachment force becomesimportant. If the particle contact with liquid/air interface cannot beprovided, capillary detachment force will not be realized. In themeantime, hydrodynamic detachment force will still be present. Since thesliding velocities of surface flow entities span a wide range of values,it is believed that both mechanisms may operate together sometimes orone may dominate over the other depending on the channel diameters andoperating conditions.

Capillary detachment force compared with bulk liquid flow: Thehydrodynamic detachment force F_(lf) created by a bulk liquid flow isexpressed by the following equation:F _(lf)=24πηU _(o)(a ² /R _(t))  (9)where R_(t) is the radius of the capillary or small tubing and U_(o) isone half of the maximum velocity of the liquid flow which occurs at thecenter of the flow. Comparison of the detachment forces caused by bothbulk liquid flow and capillary interaction on a particle can besimplified as follows:F _(lf) /F _(ca)˜12Ca _(o)(a/R _(t))  (10)whereCa _(o)=η(U _(o)/σ)  (11)Applying the same parameters as used above, viscosity η is 1×10−2 cm/s,the surface tension of water σ is 50 g/sec²(dynes/cm), and assuming themaximum bulk liquid velocity is 200 cm/sec (U_(o)=100 cm/sec), Ca_(o) isabout 0.02. The hydrodynamic detachment force of liquid flow is order ofmagnitude weaker than the capillary detachment force.

Not wishing to be bound by this explanation, it is believed that bothdetachment mechanisms may operate depending on the nature ofcontaminants and the operating conditions, including the composition ofthe cleaning liquid used according to this invention.

In this mechanism of detachment, the meniscus formed at the leading edgeof the fragment or drop makes contact with the contaminant and exerts acapillary force on the contaminant directed at least to some extent awayfrom the surface of the channel (proportional to the normal component ofsurface tension force acting on the effective contact area). Thisdetachment force may be expected to be a function of the surface tensionof the liquid, the size of the contaminant (contact perimeter) and itswettability (contact angle). This force may be sufficient to detach thecontaminant from the surface depending on the strength of the adhesiveforce holding the contaminant to the channel surface. It is believedthat capillary flotation becomes increasingly effective when theadvancing contact angle approaches 90 degrees or greater and thecontaminant particles are below about 10 μm, especially below 5 μm. Itis further possible that a receding contact angle of a sliding liquidentity or fragments can also generate such detachment forces.

The solid-liquid-gas interface may occur at either an advancing edge ofa liquid entity, i.e., when a dry local region of the surface isbecoming wet, or a retreating edge of a liquid entity i.e., when a wetlocal region of the surface is becoming dry. It is further noted thatadvancing and receding may generally coincide with the general directionof flow along a passageway or along the flow of a rivulet, but also theadvancing and receding could also be associated with a component ofmotion transverse to an overall direction of flow along the length of apassageway. A representative form of transverse motion is meandering asdescribed elsewhere herein. The motion of the liquid which causes theadvancing or receding contact angle may be either along the general flowdirection of the passageway, or may be perpendicular to the general flowdirection of the passageway, or may be some combination of the twodirections. All of these are illustrated in FIG. 2 a-2 d and also inFIG. 3 a.

When the moving liquid entity provides, through either of thesemechanisms or any combination thereof or any other mechanism, asufficient force to detach a contaminant from the wall, the contaminantcan then be swept along by the sliding liquid entity or drop or rivulet.The detached contaminant may be either moved along by the trailing edgeof the liquid entity or may be captured at the liquid/gas interface ofthe liquid entity and thereby moved along. For either of these transportprocess it may be helpful that the receding contact angle is non-zero,i.e., the trailing edge of the surface flow entity can not be draggedout to form a trailing liquid film. The non-zero receding contact angleis believed to be more important in preventing film formation on thetrailing surface than is the transport mechanism. The role ofsurfactants in the cleaning liquid is essential to controlling theadvancing and receding contact angles of surface flow entities on thewall of the passageway. The surface hydrophobicity of the passagewayalso plays a role along with surfactant composition in determining thecontact angle and on deciding the wet-dry condition during rivuletdroplet flow.

Flow Regimes

One particular flow mode which can provide cleaning action is rivuletflow. In rivulet flow, a significant portion of the liquid can existattached to the internal surface of the passageway and able to move inthe general direction of the gas flow. At least some of the liquid canexist in the form of rivulets extending generally longitudinally alongthe direction of flow. Portions of the internal surface of thepassageway which are not in actual contact with the rivulet may besubstantially dry.

Rivulet flow has been studied in the case of liquid flowing down asmooth inclined plane under the action of gravity in an environment ofstationary gas. (See for example by P. Schmuki and M. Laso, On thestability of rivulet flow, J Fluid. Mech. (1990) vol 215, pp 125-143).Rivulet pheonomena are also described in “Meandering rivulets on aplane: a simple balance between inertia and capillarity?” by Nolwenn LeGRrand-Pitiera, Adrian Daerr, Laurent LIMAT Feb. 2, 2008arXiv:physics/0510089v2 [physics.flu-dyn] 7 Nov. 7, 2006; and inLawrence Berkeley National Laboratory Paper LBNL 54681, 2004,“Constraints on flow regimes in wide-aperture fractures” by Teamrat A.Ghezzehei (http://repositories.cdlib.org/lbnl/LBNL-54681); and in Streammeanders on a smooth hydrophobic surface, by Takeo Nakagawa and John C.Scott, J. Fluid Mech. (1984), vol. 149, pp. 89-99; and in Rivuletmeanders on a smooth hydrophobic surface, by T. Nakagawa, Int. J.Multiphase Flow, Vol. 18, No. 3, pp. 455-463(1992). Most of thesereferences have studied rivulet flow down a flat inclined planesurrounded by stationary gas.

Several of these references categorize flow in these situations ashaving any of several regimes. Three of the several variables involvedare inclination angle of the plate, and liquid flowrate, and contactangle of the liquid with the surface. In general, these variables havesomewhat related effects which might be thought of as some indication ofincreasing energy or activity level. In the least active situation,which can occur for some combination of low inclination angle and lowliquid flowrate, flow of liquid entities tends to be substantiallystraight. This is a stable situation.

At a somewhat larger liquid flowrate or inclination angle, there beginto be meandering shape of the liquid flow, which may change shape as afunction of time. A meandering rivulet is illustrated in FIG. 3 b, takenfrom the Schmuki reference.

The path of such a rivulet is curved in a somewhat irregular shape.Furthermore, it has been observed that a rivulet of liquid flowing downa smooth inclined plane can spontaneously “meander” or move in a zig-zagfashion in a direction perpendicular to the general direction of flow ofthe liquid, as a function of time. In other words, the shape of therivulet changes. The situation may be such that the rivulet dynamicallychanges its position on the surface, possibly in a somewhat random orunstable manner as shown in FIG. 3 a. In some situations it is possiblethat rivulets meander because of an instability which could be thoughtof as resembling the instability of a water-discharging hose whose endis unsecured, causing the hose to whip around somewhat randomly. Thiscan be thought of as related to Rayleigh or other type of hydrodynamicinstability. Such a hydrodynamic instability may depend in a complexfashion on the liquid flow rate, local contact angles (both advancingcontact angle and receding contact angle), liquid viscosity, and inclineangle of the flat plate among other things. In the paper byGrand-Pitiera, it is described that there is a “second critical flowrateQc2” above which the shape of the meander is unstable and therefore theshape of the rivulet dynamically changes.

For purposes of cleaning interiors of passageways, it is believed thatmeandering rivulet flow is useful. In particular, the meandering ofrivulets in which the position changes as a function of time is believedto be useful. It is particularly believed to be useful when the surfacenext to the rivulet is dry, thereby providing a three-phase contactinterface which moves as shown in FIG. 3 a. In this case the advancingand receding contact angles play a definite role regarding whether arivulet is formed and the shape of the rivulet on the surface of thepassageway.

Yet another feature of this flow situation is noted in several of theabove references. As the energy or activity level increases stillfurther beyond what has already been described, there is a regime inwhich the flow restabilizes and again basically moves in straight pathsor approximately straight paths. Thus, in order to achieve dynamicallymeandering rivulets, it is not just a matter that certain parametersmust be above a threshold, but rather the somewhat more complicatedcriterion that certain parameters must be above one threshold while alsobeing below another threshold.

Differences Between Rivulets on a Flat Plate and Rivulets Inside aChannel

The literature referred to is for the situation of liquid flowing downan inclined flat plate surrounded by stationary gas. Relevant situationsfor cleaning endoscope channels or other luminal medical devices differfrom this situation. The situation of a rivulet flowing in an interiorof a horizontal passageway differs from the flat plate example inseveral ways. A rivulet on the interior surface of a passageway isillustrated in FIG. 4. One difference is that the passageway beingcleaned may overall be substantially horizontal, which is a typicalorientation of a passageway of an endoscope during cleaning. (This isnot the only possible orientation of a passageway of an endoscope duringcleaning; other possible orientations are discussed elsewhere herein.)Use of a horizontal orientation would remove the incline which waspresent in the flat plate situation as a driving force for forwardmotion of the liquid. As a substitute driving force for forward motionof liquid, there may be provided a gas flow inside the passageway alongthe length of the passageway. In such a situation, the gas may flowthrough the passageway at a velocity that is higher than the velocity ofthe liquid entities attached to the internal wall of the passageway, andmay thereby exert a drag force on the liquid entities urging them toflow along the passageway. Rivulets may move generally along thedirection of the gas flow, but due to meandering, rivulets may also havesome variation of their overall position. For example, rivulets canmeander so as to attain some motion along the internal surface of thepassageway in a direction transverse to the direction of the gas flow.

Another difference is that, with the interior of the passageway beingcurved, in order for a rivulet at the bottom of the passageway (i.e., atthe lowest elevation) to meander transversely to the longitudinaldirection of the passageway, the rivulet would have to gain elevation inorder to move transversely, i.e., it would have to climb the walls ofthe passageway by working against the force of gravity. For liquid togain elevation requires work. Thus, it may be more difficult for arivulet to move transversely inside a curved-cross-section passagewaythan it would be for a rivulet to simply move transversely on a flatplate without gaining elevation due to the transverse movement. Yetanother difference is that there may be issues related to whether thepassageway can provide sufficient cross-sectional area for gas flow, orwhether a liquid entity might tend to occupy the entire cross-sectionalarea of a particular small-diameter passageway.

It is further believed that, in a passageway that is at least somewhathorizontal, a rivulet which tends to concentrate at the bottom of thepassageway provides sort of a reservoir or source of liquid forgenerating fragmentary rivulets that may climb up the walls of thepassageway. It is also believed that when a rivulet overtakes any otherliquid entity so that the liquid entity merges with the rivulet, therivulet may provide bulk transport that brings detached contaminantsfrom the other liquid entity to the main rivulet at the bottom of thepassageway. The main rivulet may thus serve to rapidly transportdetached contaminants through the remaining portion of the passagewayand out of the passageway.

Further Liquid Entities, and Conditions

Various forms of liquid entities and flow regimes are furtherillustrated in FIGS. 5 a, 5 b and 5 c. These include rivulets asdiscussed but also other liquid entities as well. Still other liquidentities besides those illustrated schematically in FIG. 5 a are alsopossible.

A simple meandering rivulet is illustrated as entity 8 of FIG. 5 a andalso as entity B of FIG. 5 b. Although some rivulets may remain as asimple meandering rivulet, there is also the possibility that rivulets,because they involve instabilities, can fragment or break intosub-rivulets. This is illustrated as entity 6 of FIG. 5 a, and isillustrated in illustration C of FIG. 5 b.

Kinking of a rivulet or subdividing of a rivulet into additionalrivulets is also believed to be a useful cleaning mechanism. In general,multiple rivulets may sweep more area than a single rivulet. Theinstability which causes rivulets to meander may also be at least partlyresponsible for rivulets breaking into sub-rivulets.

The breaking up of rivulets does not have to end with sub-rivulets butcan still further lead a rivulet or a sub-rivulet to break up into arivulet fragment. Rivulets or sub-rivulets can further break intoisolated threads or “rivulet fragments.” This is illustrated as entity 4of FIG. 5 a, and can also be seen in illustration D of FIG. 5 b. Theserivulet fragments, although not contiguous with the main bottom rivuletor meandering segments nevertheless may move along the internal surfaceof the tube under the drag force of the flowing gas.

It is still further possible that a rivulet, sub-rivulet or rivuletfragment can further break up into a succession of drops, which maycontinue to slide along the surface. This can be referred to as a lineardroplet array. This is illustrated as the group of three of entity 2 inFIG. 5 a, and can also be seen in illustration D of FIG. 5 b. Such dropsmay exist on the internal surface of the passageway and may be able tomove along the internal surface of the passageway. However, it isbelieved that in general rivulets may be able to move at a greatervelocity than isolated droplets and may be able to sweep at a greatervelocity than isolated droplets, and may therefore accomplish cleaningfaster than droplets. For example, rivulets may be more able to sweepthe surface with a three-phase interface in a direction transverse tothe overall flow direction, and sub-rivulets or rivulet fragments mayalso be able to sweep in the direction of longitudinal motion. Dropletsmay move just in the general direction of flow and may sweep in thatdirection, but perhaps at a smaller rate of motion and sweeping comparedto rivulets.

All of these liquid entities, and any others that might form, cancontinue to move along the internal surface of the passageway along thelongitudinal direction or transversely or any combination thereof, andcan sweep passageway internal surface as they do so.

It is further possible that a meandering rivulet may overtake andswallow up isolated droplets or arrays of droplets, may swallow up arivulet fragment or branched rivulet. These entities may then re-join alarger rivulet. Such a process may be useful also for providing bulktransport of detached contaminants out of the passageway being cleaned.

Any of these entities may be referred to as a sliding or moving liquidentity.

This process may in effect be repeated many times during the cleaningthe surface of the passageway. Another possible advantage of meanderingrivulet would be to remove liquid film from the surface and providesnecessary conditions for cleaning with the three phase contact interfaceby other moving liquid entities.

It is believed, although it is not wished to be restricted to thisexplanation, that when a rivulet or other liquid entity changesposition, and a previously dry piece of surface becomes wet as a rivuletreaches it, or when a rivulet leaves a surface which it has wetted,there may be generated a force to dislodge a contaminant from thesurface.

At a still greater level of detail, it can be realized that the gasflowing longitudinally in the passageway is compressible. For a constantcross-section passageway and a generally constant temperature, gas at amore upstream location generally has a larger density and smallervelocity and gas at a more downstream location has a smaller density anda larger velocity. Thus, the conditions which might drive motion of therivulets (either longitudinally or transversely) and which mightinfluence the formation of liquid entities in general are not identicaleverywhere along the length of a passageway. It has been discoveredduring the present work that the flow parameters which produced optimalrivulet flow and fragmentation for cleaning depended among other things,upon the internal diameter and length of passageway being cleaned,position along the length of the passageway, and the surfactantcomposition of the cleaning liquid (FIG. 5 c). This is furtherillustrated elsewhere herein.

Taking various considerations into account, there are describedelsewhere herein conditions that are favorable for the formation ofrivulet droplet flow such as meandering rivulets, fragmenting rivulets,drops and other forms of sliding liquid entities that are favorable forcleaning. The apparatus may be such as to deliver liquid flowrate and agas flowrate appropriate to operate in the desired regime at least someplaces along a passageway.

It has been experimentally found (photographically) in the present workthat at 30 psig gas pressure, for a 1.8 mm inside diameter passageway 2m long, the longitudinal sliding velocity of a rivulet can be, from 1cm/sec to 10 cm/sec with a mean of perhaps 2 to 3 cm/sec. For a 2.8 mminside diameter passageway, the longitudinal sliding velocity of arivulet can be, from 5 cm/sec to 20 cm/sec with a mean of perhaps 12.5cm/sec. For a 3.8 mm inside diameter passageway, the longitudinalsliding velocity of a rivulet can be, from 7 cm/sec to 35 cm/sec with amean of perhaps 22 cm/sec. These velocities were measured for liquidentities having dimensions of the order of 100 microns. Larger entitiescould have even faster velocities.

Corresponding to these, for a meandering rivulet, the transversevelocity may be as large as 25% to 50% of the longitudinal velocity.

For still other modes of flow or cleaning, other than meanderingrivulets, it is possible to achieve still larger velocities of surfaceflow entities. Also, for a flow mode such as plug flow, largervelocities of moving meniscus or surface flow entities are alsopossible.

The overall effect of the sliding of these surface flow entities may bethe sweeping of the surface of the channel by multiple movingthree-phase contact interfaces and menisci. The internal surface of thepassageway may be swept with a variety of liquid surface flow entitiesincluding meandering rivulets, sub-rivulets, rivulet fragments, lineardroplets arrays and individual droplets of various sizes all in contactwith the surface of the channel. Each of these entities may have anassociated three-phase gas/liquid/solid contact interface and meniscus.It is believed, although it is not desired to be limited to thisexplanation, that the existence of a three-phase boundary and air/waterinterface (meniscus) create localized forces that can act to detach acontaminant from a surface. This may especially be true if thethree-phase boundary is moving relative to the contaminant. The threephases may be the solid contaminant, and an edge of a liquid, and a gas.At least some of the surface may be dry or nearly dry some of the timeduring the cleaning process. It can be helpful if the surface of thechannel is at least somewhat hydrophobic. The three phases can also bethe liquid surface, the gas, and the solid surface which may be drywhere it is not wetted by the liquid entity.

It is possible that different flow regimes may exist in differentportions of a given passageway, and flow may transition from one flowregime or mode to another. At any given location, more than one flowregime may coexist, e.g., some drops and some rivulets. At differentlocations along a passageway, different regimes or combinations ofregimes may exist.

It is the nature of multi-phase flow to be complex and somewhatstatistical in nature and somewhat unpredictable, and more specificallyfor the geometry and behavior of liquid entities that are attached tothe surface of the channel to be somewhat statistical in nature andsomewhat unpredictable. Some of the behavior may be driven by fluidinstabilities on the surface of the passageway (rather than bulk effectsin the core of the passageway) which are inherently somewhatunpredictable. Empirical data is important in the science of multi-phaseflow.

As examples of what can be observed, FIG. 5 b shows both photographicexamples and line drawings of five different types of flow. These areapproximately in order of wetness. FIG. 5 b Illustration A showsisolated droplets, which would be the case for a flow of liquid and gaswhich is somewhat dry, with not enough liquid to sustain a stream. FIG.5 b Illustration B shows a meandering rivulet. Occasional isolateddroplets are also shown. FIG. 5 b Illustration C shows meanderingrivulet which also is fragmenting into sub-rivulets. FIG. 5 bIllustration D shows rivulets that co-exist with linear droplet arrays.In this illustration, the rivulets have somewhat straightened out. FIG.5 b Illustration E shows a flow with so much liquid that the tube wallwhich is mostly wet and there are essentially no dry regions to helpdefine rivulets, droplets or any other liquid entities.

At relatively high liquid flow rates or gas flowrates is yet anotherpossible flow regime which is not illustrated, namely foam. In presentsituations, if foam forms anywhere it tends to form near the exit of thepassageway, and may extend for some distance back toward the inlet. Iffoam forms, the passageway surface where foam is present can becomecovered with liquid film with no chance to form three-phase contactinterface. For present purposes, it has been found that generally foamsuppress cleaning employing the present method. This is probably becausethe presence of foam discourages the formation of discrete wet and dryregions exhibiting a contact interface therebetween. Also, the presenceof foam can increase overall flow resistance for gas flow. The formationof foam can be significantly influenced by the nature of the surfactantused, as discussed elsewhere herein.

FIG. 5 c shows the same illustrations arranged in lengthwise sequence.Sometimes some of the same sequence is observed spatially as oneprogresses downstream along a passageway. The liquid first flow asmeandering rivulet, then as rivulets that break up, and later asstraight rivulets. This sequence of events may be driven at least inpart by the tendency for the gas velocity to increase as one progressesdownstream along a passageway. Eventually as one progresses downstreamthe gas velocity increases beyond an upper threshold for meandering andthe rivulets or rivulet fragments become generally straight. However,this is only representative, and events do not have to happen exactly asdescribed here.

Rivulet droplet flow (RDF) may be considered to comprise either rivuletsor droplets or both in any combination. Rivulet droplet flow may includeany one or more of meandering rivulets, sub-rivulets, fragments ofrivulets, and arrays of drops, and individual drops. Rivulet dropletflow may be formed, as described elsewhere herein, by supplying liquidand gas to a passageway wherein both the liquid and the gas are suppliedat substantially constant flowrates. Alternatively, as also describedelsewhere herein, rivulet droplet flow may be formed by supplying liquidand gas to a passageway such that the flowrate of at least one of thesupplied liquid and the supplied gas is time-varying. This can includeplug rivulet droplet flow.

When it is discussed herein that it is desirable for a surface tode-wet, this can be accomplished through either or both of the followingmechanisms. If by its nature a surface is sufficiently hydrophobic withrespect to the liquid passing over it, the surface may becomesubstantially dry as soon as a liquid entity finishes passing over it.On the other hand, it is possible that a surface may still be somewhatwet after a liquid entity has finished passing over it, but due toevaporation the surface still becomes substantially dry with the passageof time after a liquid entity has finished passing over the surface.When the term dry is used herein, it is intended to include any of thesemeanings.

Photographs and Flow Maps

The regimes of gas and liquid flow have been studied empirically bycarrying out systematic microscopic observations through straighttransparent Teflon® tubes of various diameters under various liquid andgas flow rates at different distances from the inlet of the tube. Thishas included still photography and high-speed motion photography as wellas stroboscopic illumination with multiple-exposure photography.Photographs were taken looking vertically downward through the wall of aclear horizontally oriented tube. By varying the focal plane of theoptics, the flow along either the top or bottom hemicylindrical surfacesof the tube could be observed. All photographs presented here were takenof the top surface. Sequential images as a function of time could beanalyzed so that the flow and flow entities could be analyzed over timeand their movements tracked.

Experimental observations are further illustrated in FIGS. 6 a, 6 b and6 c, which is only a small subset of a large amount of photographicdata. For the illustrated photographs, the gas flow was air. The flowexited the downstream end of the passageway at atmospheric pressure. Thegas flow was supplied to the inlet of the passageway at a pressure of 30psig. For the photographs and the flow regime maps, both liquid and gaswere supplied to the passageway at room temperature (approximately 20°C.). The length of the passageway was 2 m. All of these photographs aretaken for a particular diameter of passageway, which was 4.5 mm. Asdiscussed elsewhere herein the fluid mechanics can be influenced bydetails of the surfactant which is added to the water.

For generating the photographs in FIG. 6, the test solution was watercontaining the following additives:

-   Sodium Triphosphate, (Fisher Scientific) 30 g/L;-   Sodium Silicate, (Fisher Scientific) 1.3 g/L;-   Tomah AO-455 made by Air Products—0.24 g/L;-   Surfynol 485W made by Tomah-Air Products—0.36 g/L.    The surface tension of this composition at room temperature was    approximately 38 to 44 dyne/cm. It is believed that this composition    gives good fragmentation and not so many surviving sub-rivulets, but    rather rivulet fragments.

FIG. 6 shows photographs of flow conditions in a passageway having aninternal diameter of 4.5 mm. Conditions are shown at five differentlocations along a total flow length of 2 m.

FIG. 6 a shows hydrodynamic conditions for a liquid flowrate of 20milliliters/minute, which is considered to be undesirably small andtherefore less effective for cleaning (treatment number is small). Insuch a situation, there is a fairly large proportion of isolateddroplets rather than rivulets, and the isolated droplets slide along thesurface at a relatively smaller velocity than the rivulets, producing aslower rate of cleaning which may lengthen process time. Cleaning mayoccur at places where the three phase contact interface passes by due tothe sliding of these liquid entities, but the fact that there are not somany of these liquid entities, and the fact that the entities are mostlydrops, which move somewhat slowly, may limit the achievement of cleaningin a reasonable time (2-10 minutes).

FIG. 6 b shows hydrodynamic conditions for a liquid flowrate of 45ml/minute, which was considered to produce good cleaning.

FIG. 6 c shows hydrodynamic conditions for a liquid flowrate of 70ml/minute, which is considered to be undesirably large and thereforeless effective for cleaning. In such a situation, the internal surfaceof the passageway may be wet a large fraction of the time so that thereis not a sufficiently frequent occurrence of a dry or substantially drysurface so as to achieve a moving three-phase contact interface. This isbelieved to limit the achievement of cleaning if the surface is as wetas is shown in FIG. 6 c. It is not wished to be limited to theseexplanations, however.

Conditions which are conducive to achieving cleaning by movingsolid-liquid-gas interfaces flow can be further described by parameterdiagrams which describe a flow regime for particular input flow anddimensional conditions. The photographic information such as illustratedin FIG. 6 a, 6 b, 6 c were all taken for a particular passageway insidediameter (4.5 mm) but even that information provides only a few of themany data points needed to construct such a diagram.

For reference, the conditions illustrated in FIG. 6 a (a low flowrate of20 milliliters/minute) are characterized as being more in the nature ofisolated droplets (sparse) rather than rivulets. The isolated dropletshave slower sliding velocity than rivulets and there are fewer of them,and for these reasons there is somewhat limited opportunity toaccomplish cleaning by moving three-phase contact interfaces. Theconditions illustrated in FIG. 6 b (a medium flowrate of 45milliliters/minute) are characterized as being rivulet droplet flow withsome rivulet fragments and some drops, which provides good cleaning. Therivulets sweep area with three-phase contact interfaces at a desirablerate and therefore accomplish cleaning. The conditions illustrated inFIG. 6 c (a high flowrate of 70 milliliters/minute) are characterized asbeing overly wet flow, such that there are not so many places on thepassageway internal surface that are actually dry at any given time, andfor that reason there is somewhat limited opportunity to accomplishcleaning by moving three-phase contact interfaces.

As can be understood, a multitude of such observations are used toconstruct a flow diagram such as is given in FIG. 7. Such a diagram maybe unique to a particular passageway inside diameter or range of insidediameters. Flow regime maps for five different passageway insidediameters are given in FIGS. 7 a through 7 e.

As mentioned, the photographs were taken for an inlet air pressure of 30psi, which for many channels of many endoscopes is approximately amaximum allowable input pressure. In order to have flow conductive tocleaning, it may be aimed that conditions be chosen which providerivulets and rivulet fragments in much of the passageway and droplets inplaces where rivulet flow is not achieved. This may be termed rivuletdroplet flow. As can be seen from the maps, choosing a particular liquidflowrate does not guarantee the same flow regime will exist all the wayfrom the beginning (inlet) to the end (exit) of the passageway. Also,the five maps are presented for five different passageway insidediameters, and it can be seen that the maps differ from each other bothqualitatively and quantitatively as a function of the inside diameter ofthe passageway.

In order to help summarize and collect the information presented inFIGS. 7 a through 7 e, some representative useful ranges of liquidflowrates from FIGS. 7 a through 7 e are selected and are plotted inFIG. 8. These are flowrates which provide rivulet droplet flow for asignificant portion of the length of the particular passageway, althoughnot necessarily the entire length of the passageway. These flowrates aresomewhat optimum for achieving rivulet droplet flow for the respectivepassageway inside diameter, although it is not to be implied that theseare the only liquid flowrates that could be useful for cleaning. It alsomay be kept in mind that these data may be somewhat specific to stillother operating parameters including but not limited to surfactantcomposition, flowpath length, inlet gas pressure, and other parameters.

Although FIG. 8 presents specific numerical values of liquid flowrateassociated with specific numerical values of passageway inside diameter,it is also possible to describe desirable liquid flowrates in terms ofvolumetric liquid flowrate per unit of perimeter of the passageway. Thisis in recognition of the fact that the liquid flow primarily attaches tothe perimeter of the passageway.

For example, for a relatively large passageway of inside diameter 6 mm,a representative useful range of liquid flowrate is 30 to 65 ml/minute.For such a passageway, the inside perimeter is 18.84 mm. Thecorresponding liquid flowrate per unit of internal perimeter is from30/18084 or 1.59, to 65/18.84 or 3.45 ml/minute per mm of perimeter.

For a passageway of inside diameter 4.5 mm, as depicted in FIG. 6, arepresentative useful range of liquid flowrate is 15 to 40 ml/minute.For such a passageway, the inside perimeter is 14.13 mm. Thecorresponding liquid flowrate per unit of internal perimeter is from15/14.13 or 1.06, to 40/14.13 or 2.83 ml/minute per mm of perimeter.

Similarly, for a 2.8 mm inside diameter passageway, a representativeuseful range of liquid flowrate is 15 to 25 ml/minute. This passagewayhas an inside perimeter of 8.79 mm. The liquid flowrate per unit ofinternal perimeter is 15/8.79 or 1.71, to 25/8.79 or 2.84 ml/minute permm of perimeter.

Similarly, for a 1.8 mm inside diameter passageway, a representativeuseful range of liquid flowrate is 6 to 10 ml/minute. This passagewayhas an inside perimeter of 5.65 mm. The liquid flowrate per unit ofinternal perimeter is from 6/5.65 or 1.06, to 10/5.65 or 1.77 ml/minuteper mm of perimeter.

Similarly, for a 0.6 mm inside diameter passageway, a representativeuseful range of liquid flowrate is 5 to 10 ml/minute. This passagewayhas an inside perimeter of 1.88 mm. The liquid flowrate per unit ofinternal perimeter is from 5/1.88 or 2.66, to 10/1.88 or 5.32 ml/minuteper mm of perimeter.

Combining these observations, it can be seen that thisperimeter-normalized liquid flowrate clusters in a range of from about1.5 to 4 milliliters/minute per mm of perimeter, or, defined slightlymore broadly, in the range of from approximately 1 to approximately 5milliliters/minute per mm of perimeter.

It can also be noted that for achieving meandering rivulets, a desirablegas velocity may be in the range of approximately 5 m/s to approximately15 m/s at least somewhere along the length of the passageway. Meanderingrivulets are useful but are not absolutely required for achieving goodcleaning in a reasonable time. Another gas velocity range that may beuseful for cleaning is a broader range that is appropriate for achievingfragmentation and sliding liquid entities or surface flow entities onthe wall of the passageway may be from approximately 2 m/s to 80 m/sdepending on the diameter of the passageway.

It can be noted that the flow regime can depend on at least the liquidflowrate, the gas flowrate, the position along the length of thepassageway, and the inside diameter of the passageway. The flow regimecan depend on the overall length of the passageway at least because theoverall length can affect the gas flowrate given a typical maximumsupply pressure of the gas. Surfactant composition and concentration canalso affect the flow regime. The data presented in FIGS. 6, 7 and 8 wereobtained for input liquid flow and gas flow which were both steady withrespect to time.

Still further data about flow regimes is presented in FIG. 9. It may berecalled that FIGS. 6, 7 and 8 all are for data taken at an inlet airpressure of 30 psig. That was a maximum allowable air pressure fortypical channels of typical endoscopes. However, it is also possible tooperate at inlet air supply pressures less than the maximum allowablepressure. This may be considered in view of the suggestion from theliterature that meandering may occur within a specific operating range,rather than there being a simple threshold above which meandering alwaysoccurs. This is discussed elsewhere herein. For the data presented inFIG. 9, both inlet air pressure and liquid flowrate were varied. Again,several different passageway diameters were used as indicated. Thepassageway length was 2 meters. The composition of the liquid was thesame as was used for FIGS. 6, 7 and 8.

It can be appreciated from FIGS. 9 a and 9 b that it may not be possibleto achieve meandering rivulet flow everywhere along the length of thepassageway, especially with a single liquid flowrate. Also, meanderingoccurs for some gas supply pressures such as moderate pressures but notfor other pressures such as more extremely high or low gas supplypressures. Meandering rivulet flow is useful for cleaning, but is notthe only useful flow regime. Rivulet droplet flow is also useful.Straight rivulet flow is believed to be not so useful for cleaning,because not much sweeping occurs nor does fragmentation of rivuletsoccur. Foam/film also is not believed to be useful for cleaning becauseit basically impedes flow and perhaps also keeps the surface wet.However, it is not wished to be limited to this explanation. In FIG. 9,the following notation is used. Y means achieving meandering rivuletflow suitable for cleaning. R means RDF (rivulet droplet flow) which isbelieved to be useful for cleaning; S means a straight rivulet with nomeandering, which is believed to be not so useful for cleaning; F meansfilm/foam, which is believed to be not so useful for cleaning.

It can be appreciated that FIGS. 9 a and 9 b illustrate an observationthat is consistent with the observations of the fluid mechanicsliterature for inclined flat plates in stationary gas. Achievingmeandering rivulets is not just a matter of operating above a certainlower threshold so as to enter a region of instability. In addition tothe existence of a lower threshold, there can also be an upperthreshold, such that it is also necessary to remain below the upperthreshold in order to have meandering rivulets.

One parameter that the upper threshold can pertain to is gas velocity.It has been discussed elsewhere herein that as compressible gas flowsalong a long passageway, the gas velocity increases. Thus, it ispossible that even if meandering rivulets exist in a middle portionalong a length of a passageway, as one approaches the exit of a longpassageway, the gas velocity may become so large that it re-stabilizesthe rivulets. It is furthermore possible that even if meanderingrivulets exist in a middle portion along a length of a passageway, thegas velocity very near the inlet may be too small to create meanderingrivulets. This helps explain why in some regions along the length ofpassageways in FIGS. 9 a and 9 b, meandering rivulet flow exists only atcertain places along the passageway.

Gas velocity is somewhat related to supplied inlet gas pressure.Therefore, it is possible that a supplied inlet gas pressure could betoo small to create meandering rivulets anywhere in the passageway, orcould be too large to create meandering rivulets anywhere in thepassageway. Similarly, it is possible that a supplied liquid flowratecould be too small to create meandering rivulets anywhere in thepassageway, or could be too large to create meandering rivulets anywherein the passageway. These conditions also are a function at least of theinside diameter of the passageway being cleaned. These criteria also area function of the surfactant and composition of the cleaning liquidused.

For typical operating conditions, a range of gas velocity that isconducive to meandering rivulets is from approximately 5 m/sec toapproximately 15 m/s. In an embodiment of the invention, the operatingconditions may be such as to operate in this range for at least aportion of the length of the passageway.

It can also be observed from FIG. 9 that there are optimum values ofliquid flowrate. If the liquid flowrate is too small or too large,meandering rivulets may not be achieved or may only be achieved for alimited portion of the length of the passageway.

It is believed, although it is not wished to be limited to thisobservation, that for larger inside diameters in the range of interest,the range of liquid flowrates acceptable for achieving cleaning isrelatively wide, and for smaller inside diameters in the range ofinterest, the range of liquid flowrate acceptable for achieving cleaningis relatively narrow.

In view of the observations such as presented in FIGS. 6, 7, 8 and 9, inembodiments of the invention, the apparatus may be configured so as toprovide a gas flowrate and a liquid flowrate that are in a properrelationship to each other so as to provide a desired rivulet-dropletflow regime of liquid and gas. In view of the observations such aspresented in FIG. 9, in embodiments of the invention, the apparatus maybe configured so as to provide a gas flowrate and a liquid flowrate thatare in a proper relationship to each other so as to provide a meanderingrivulet flow regime of liquid and gas, at least in some portions of thelength of the passageway. However, meandering is not essential toachieving good cleaning.

The flow regime may be such as to provide rivulets which slide along theinternal surfaces of the passageway being cleaned, or at least on aportion of the internal surfaces of the passageway being cleaned. It isfurther possible that rivulets may subdivide into sub-rivulets. Suchdivision into sub-rivulets may occur at kinks or points of curvature ofa rivulet. It is possible that sub-rivulets may further break intorivulet fragments, being still smaller than sub-rivulets. It is possiblethat rivulet fragments may in turn break into an array of drops. All ofthese entities may be able to move along the internal surface of thepassageway being cleaned. The flow regime may be such as to providemeandering rivulets which are unsteady in time on the internal surfacesof the passageway being cleaned, or at least on a portion of theinternal surfaces of the passageway being cleaned, although meanderingis not essential.

As still further guidance for achieving appropriate flow regimes, it ispossible that flow of liquid cleaning medium suspended as droplets inthe gas prior to entering the passageway may be less than 10% of thetotal flow of liquid cleaning medium, and may be less than 1% of theflow of liquid cleaning medium. That is to say the volume of liquidflowing through the internal channel may be predominantly in the form ofrivulets and surface flow entities fragmented from these rivulets.

It is possible that at the exit of the passageway, flow of liquidcleaning medium suspended as droplets in the gas may be less than 50% ofthe total flow of liquid cleaning medium, or less than 10% of the flowof liquid cleaning medium, or less than 5% or less than 1%.

It is possible that at the exit of the passageway, the amount of liquidwhich is in the form of foam may be less than 10% of the total flow ofliquid, or less than 1% of the total flow of liquid.

Multi-Stage Cleaning

As described, an aim can be to achieve a desired flow regime such asrivulet flow and moving liquid flow entities with three-phase contactinterface essentially everywhere along the length of the passageway. Ifa desired flow regime is achieved at only a portion of the length of thepassageway, that can still be useful, but achieving the desired flowregime everywhere along the length of the passageway would be moreconvenient. This can be adjusted, among other ways, by adjusting theliquid flow rate.

However, it may not be possible to provide desired cleaning conditionsfor the entire length of the passageway using a single set of operatingconditions. If this is the case, then another possible strategy may beto perform cleaning of a first portion of a length of a passageway usinga first set of parameters that are appropriate for cleaning a firstportion of the length of the passageway, followed by performing cleaningof a second portion of the length of the passageway using a second setof parameters that are appropriate for cleaning the second length of thesame passageway. Cleaning conditions for different passageways coulddiffer in inlet air pressure, or in liquid flowrate, or both, or inother parameters.

If such a multi-stage cleaning process is used, it is possible that theportion of the passageway which is cleaned first may be upstream of theportion of the passageway which is cleaned later. That way, contaminantsand debris which are dislodged from the later-cleaned portion of thepassageway may be expected to wash downstream and out of the passagewaywithout possibly contaminating the earlier-cleaned portion of thepassageway.

It can be appreciated that all of the data presented in FIGS. 6, 7, 8and 9 are for constant operating conditions, i.e., constant inputtedflowrate of liquid and constant inputted flowrate of gas.

Additional Strategies for Specific Portions of Internal Surface, andUnsteady Flow Inputs

It may be appreciated from the preceding discussion that for ahorizontally oriented passageway (which is a possible orientation of achannel of an endoscope being cleaned), it may be more difficult forrivulets to reach the upper surface (ceiling) of a substantiallyhorizontal passageway than it is to reach lower-elevation portions. Thismay be especially true for a relatively large-diameter passageway. Thus,it is possible that the ceiling could be undesirably dry. In addition,there is another basic possible problem, which is that it is likely thatthe lowest-elevation portion of the passageway (floor) is wet anundesirably large percentage of the time during a cleaning process, andtherefore the floor may be less likely to receive sweeping bythree-phase contact interfaces involving alternation of wetness anddryness.

Still another consideration, apart from comparison between floor andceiling, is that a passageway may experience an inlet or developing-flowregion where desired flow regimes might not be immediately establishedat the inlet of the passageway, at least for certain operatingconditions. This phenomenon is illustrated in FIGS. 9 a and 9 b, and itcan also be somewhat seen in FIG. 6 that flow regimes can change as afunction of position along the length of the passageway.

Accordingly, another basic strategy is that the apparatus may be such asto provide time-varying wetness and dryness conditions for certainportions of the passageway internal surface by providing time-varyinginput flow conditions. In general it is desired that the apparatusprovide liquid entities that have three phase contact interface thatwill sweep the entire internal surface of the passageway at least onceat some time or another during a reasonable cleaning time. It is alsopossible to design that the internal surface be swept multiple timesduring a treatment. Without such manipulation some sections of thepassageway may not receive sufficient treatment number as others.

FIG. 10 a illustrates, with respect to one of the flow maps of FIG. 7,that desirable rivulet droplet flow may be achieved for more downstreamregions along the length of the passageway, but are not achieved forsome of the more upstream regions of the length of the passageway. Thismay provide impetus for use of a cleaning mechanism involvingnon-steady-state input of either liquid flow or gas flow or both.

Some fluid mechanic considerations relating to surface tension areillustrated in FIG. 10 b, 10 c, 10 d, 10 e. The passageways shown inFIG. 10 b, 10 c, 10 d, 10 e are substantially horizontal, although thesame discussion is also at least somewhat applicable to passageways ofother orientation.

For passageways of a small inside diameter that contain both liquid andgas under static conditions, a possible situation is the situation inwhich a meniscus bridges across the entire cross-section of thepassageway. This is illustrated in FIG. 10 b. FIG. 10 b shows a dynamicsituation in which the liquid is moving in the direction indicated,displaying advancing and receding contact angles. (If the situation werestatic, the menisci on each sides would be essentially symmetric witheach other.)

There is also a larger range of internal dimension of passageway whichdo not support the type of meniscus illustrated in FIG. 10 b. For suchlarger passageways that contain both liquid and gas under staticconditions, the passageway cannot support a meniscus across the entirepassageway, but rather there will naturally be a configuration in whichliquid collects at the bottom of the passageway and the rest of thepassageway cross-section is substantially occupied by gas. This isillustrated in FIG. 10 c. The distinction between the situation of FIG.10 b and the situation of FIG. 10 c can be understood with reference toa critical inside diameter, which is the borderline between the twosituations. The critical inside diameter is a function of the surfacetension and other properties of the liquid. For pure water, the criticalinside diameter is approximately 1.8 mm.

For passageways having an inside diameter greater than this criticalinside diameter, it may be still possible to attain a cross-sectionfully or mostly filled with liquid, in a dynamic situation, by causingliquid to flow for a period of time, such that for at least a portion ofthe liquid flow there is liquid substantially completely filling thecross-section of the passageway. This may produce essentially a movingplug of liquid, whose meniscus sweeps internal surfaces of thepassageway. The periods of liquid flow may be separated by a periods ofgas flow that are of long enough duration to effectively separate theliquid entities from each other, and possibly also to create dryout ofpassageway internal surfaces between passage of successive liquid plugs.This is illustrated in FIG. 10 d. This pattern may be repeated as manytimes as desired. This fluid flow regime is termed discontinuous plugflow (DPF). The velocity of the moving meniscus in this case may beseveral meters per second depending on the gas pressure, tube diameterand the length of the liquid plug among other factors. The high slidingvelocities generated in this case were found to produce effectivecleaning of passageways according to the mechanisms described herein.

Referring now to FIG. 10 e, it is illustrated that as a plug progressesto a further downstream portion of a passageway, the leading face of theplug may become irregular even if the plug started out fairly regularlyshaped as shown in FIG. 10 d. This increasing irregularity of theleading face of the plug can be due to surface instabilities due togravity, Rayleigh instabilities etc. In FIG. 10 e it is also shown thatthe plug may spread preferentially toward the bottom of the passagewaydue to gravity. It is believed that irregularity at the leading edge ofthe plug can be helpful for creating liquid entities that are useful forcleaning the internal surfaces of the passageway. If at least someportion of the plug breaks up into smaller liquid entities, that isbelieved to be useful for cleaning the internal surfaces of thepassageway. This regime may be termed discontinuous plug droplet flow(DPDF).

It is still further possible that still other flow regimes can be usedwhich accomplish a moving three-phase interface using alternatingperiods of liquid flow and gas flow of liquid and gas, or other flowvariants, as described elsewhere herein. It is still further possiblethat combinations or sequences of these described fluid flow regimes maybe used, possibly also involving periods or sequences of rivulet dropletflow, in any desired sequence or combination.

Time-varying input flow characteristics are illustrated in FIG. 11.

First, in FIG. 11 there is illustrated, for reference, steady-state flowinputs such as were used for generating FIG. 6 through FIG. 9.

Next, there are illustrated various forms of non-steady-state supply ofeither liquid or gas of both, which may produce useful forms of rivuletdroplet flow under conditions other than steady-state orquasi-steady-state conditions.

One of the timelines in FIG. 11 illustrates alternating switching on andoff of gas flow and liquid flow. For example, there may be provided aliquid pulse having a duration of approximately 1 second to 3 seconds.Following a liquid pulse, in order to achieve dryout of passagewayinternal surfaces prior to re-exposure to liquid, there may be provideda duration of dry or warm or dehumidified air having a duration ofapproximately 5 seconds to 15 seconds, appropriate to achieve dryout orde-wetting of the passageway internal surface. In this timeline, at anygiven instant, either liquid is supplied or gas is supplied but neverboth. This can be described as plug flow or plug rivulet droplet flow.

It is also illustrated that it is possible to pulse either one of thesupplies while the other supply remains on. For example, liquid supplycould be pulsed while gas is remains on, or gas could be pulsed whileliquid remains on.

It is possible to perform pulsed liquid flow followed by continuousliquid flow, or in general to perform any sequence of unsteady liquidflow and steady liquid in any sequence.

Of course, even though these illustrations show one flowrate goingexactly to zero during certain time periods, for phenomena that do notinvolve dryout, it is possible for variations to be more general and notnecessarily involve decreasing exactly to zero.

As yet another possibility, it is possible to use a first gas supplypressure at a time to promote formation of liquid entities, and then tochange to another gas supply pressure for a period of time to cause themotion of these entities along the passageway. The second pressure couldbe smaller than the first, although the opposite is also possible. It isfurther possible that during whatever time a lower gas supply pressureis used in cleaning one channel, there could be performed in anotherchannel a flow that requires a relatively high gas source pressure. Thiscould be performed in such a way that the total demand for gas at anyinstant throughout the entire reprocessing cycle is less than it wouldbe if peak demands for gas flow occurred simultaneously with each other.

Various possible sequences are also described in the following Table 1A.

TABLE 1 Cycle 1 Cycle 2 Cycle 3 Pulsing Mode 1: Air OFF/Liquid ON 10 sec 8 sec 6 sec Air ON/Liquid OFF 10 sec 12 sec 3 sec Pulsing Mode 2: AirOFF/Liquid ON 10 sec  8 sec 6 sec Air ON/Liquid ON 10 sec 12 sec 3 secPulsing Mode 3: Air ON/Liquid ON 0.3-3 sec  Air ON/Liquid OFF 0.3-3 sec 

The waveforms or sequences of liquid flowrate which are repeated do nothave to be as simple as a substantially constant “on” value of flowratefollowed by a zero flowrate for the “off” situation. More generally, thewaveform of liquid flowrate could be triangular waveforms, trapezoidalwaveforms, sinusoidal waveforms, or other waveforms. The waveformsdescribing the liquid flow could have a monotonically increasingportion, optionally followed by a constant portion, and followed by amonotonically decreasing portion. There could be a dry interval betweenwaveforms of liquid flow, but more generally there does not have to besuch a dry interval. Waveforms of liquid flowrate could be repeatedidentically, or alternatively they do not have to be identical. The gasflowrate has been illustrated as being steady (constant flowrate), butit does not have to be. In this illustration, the “on” liquid flowrateis considered to be appropriate to achieve meandering rivulet flow in atleast a portion of the length of the passageway being cleaned. Thesealteration in admitting the gas and liquid in the passageway may beconsidered to permit more meandering and more fragmentation during thecleaning or rinsing cycles.

Endoscopes are frequently cleaned such that the endoscope or at least alarge portion of the endoscope is in the horizontal orientation. For anypassageway but especially for a horizontal passageway, such randompositioning of the meandering rivulet may be advantageous for achievingcleaning of the entire internal surface of the passageway. However, itis also possible that, especially in some of the larger diameterpassageways, due to gravity there may be a tendency for rivulets tospend more time than average at or near the bottom of the cross-sectionof the passageway. This may deprive upwardly-located surfaces ofcleaning because rivulets might not reach those surfaces sufficientlyoften, and those surfaces might not experience alternations of wetnessand dryness sufficiently often because of being dry a high percentage ofthe time. Furthermore, the presence of a bottom rivulet may deprivebottom-located surfaces of cleaning because those surfaces may be wet arather large portion of the time and those surfaces might not experiencealternations of wetness and dryness sufficiently often because of beingwet a high percentage of the time.

Accordingly, it is also possible to operate endoscope reprocessingapparatus such that passageway internal surfaces experience alternationsof exposure to moving three phase contact line conditions by pushingalternate periods of liquid flow and gas flow through the passageway.The period of gas flow may be sufficiently long, and the gas asintroduced may be sufficiently dry so that the internal surfaces of thechannel substantially dry out (remaining liquid film thickness is moreor less lower than the contaminant particle dimension) before the nextintroduction of liquid.

It is also possible that the period of liquid flow in this describedstrategy helps to flush out debris that has already been detached buthas not yet been moved to the exit of the passageway.

Still a further possibility is that for a certain period there could berivulet droplet flow using supplied flowrates of liquid and gas that aresubstantially steady-state, and for another period there could be a flowregime that includes any of the described regimes that involvenon-steady-state fluid supply such as pulsed fluid supply (either gas orliquid). These periods of time could be combined in any sequence orcombination.

Enhancement of Hydrodynamic Detachment by Decrease of Liquid Plug Lengthin DPF Mode

When the liquid plug is shorter than passageway length, after it isseparated from the liquid pump, it is driven by air pressure P_(a). Theresistance to flow will consist of two terms: i) resistance along theliquid plug and ii) resistance along the air portion in the passageway.Since the viscosity and density of air are significantly smaller thanthose of liquid, it may be possible to disregard the small pressure dropalong air portion of tube. This simplification becomes crude when thelength of water plug, L_(pl), is extremely smaller than compared to thelength of the passageway. This simplification can be illustrated byintroduction the nominations for pressures on plug front P_(f), plugrear P_(re) and passageway inlet P_(a), while the pressure at tubeoutlet is zero. Hence,P _(a) =P _(f)+(P _(re) −P _(f))+P _(a) −P _(re)  (16)P_(f)−0 and P_(a)−P_(re) are pressure drops within air and they may bedisregarded as being proportional to small air viscosity (or inertia).Hence, we have on r.h.s. P_(re)−P_(f), i.e. the pressure drop over plugP _(f)−0<<P _(a) ;P _(a) −P _(re) <<P _(a)  (17)HenceP _(re) −P _(f) =P _(a)  (18)There is a balance between pressure drop applied to the liquid plug andshear stress, τ, between plug and adjacent channel wall, area2πR_(t)L_(pl) where L_(pl) is the plug length. The total shear stressapplied to the plug is 2πR_(t)L_(pl)τ_(pl) is overcome due to appliedpressure P_(re)−P_(fr)=P_(a), i.e.2πR _(t) L _(pl)τ_(pl) =P _(a)(πR _(t) ²)  (19a)orτ_(pl) =P _(a)(R _(t)/2)(1/L _(pl))  (19b)This equation is valid, in particular, when the plug fills the entiretube, i.e. when L_(pl)=L_(t)τ_(t) =P _(a)(R _(t)/2)(1/L _(t))  (20a)However, at this initial moment the plug is yet not disconnected fromthe liquid pump, i.e. in this moment the plug is driven by pump pressureP_(pu)τ_(t) =P _(pu)(R _(t)/2)(1/L _(t))  (20b)For the sake of simplicity we assume thatP _(a) =P _(pu)  (21)which reduces two equations (19a) and (19b) to one. The jointconsideration of Eqs(18) and (19a) shows that they have identicalmultiplier in the bracket. The ratio of l.h.s. of these equations equalsto ratio of r.h.s., while the mentioned multiplier cancelsτ_(pl)/τ_(t) =L _(t) /L _(pl)  (22a)orτ_(pl)=τ_(t)(L _(t) /L _(pl))  (22b)Since the cleaning is caused by shear stress, the specification τ foreither laminar or for turbulent regime is excessive. The Eq(22b) isvalid for both regimes as well as for the laminar-turbulent transitionmode. The equation shows that as the plug length decrease approximately50 times, τ_(pl) increases 50 times. The further decrease L_(p1) willlead to slower increase in τ_(pl) because the requirements expressed byEq(17) fail. However, this requirement may be omitted and more generalequation can be derived. It is noteworthy to note that τ_(pl) in Eq(22b)is shear stress of liquid flow for the condition of plug flow.

In order to clarify the effect of plug length influence on cleaning byhydrodynamic detachment near the three phase contact line, we need toconsider the dependence of front meniscus velocity on plug length forturbulent or transition flow, especially for the case of suction channelbecause at 30 psi Reynolds number Re is rather high even for continuousliquid flow. For Pentax endoscope Model FG-36UX suction channel, usingliquid velocity U_(o)=146 cm/sec yields Re_(o)=(0.38×146)/0.01=5548, at35 psi. For the water channel Re_(o)=(0.18×108)/0.01=1950. Withdecreasing plug length, its velocity increases that causes Re increaseand transition to turbulent flow even for water channel. Accordingly, weneed to apply the main equation for turbulent flow in tubes, namely theequation for resistance coefficient for tube (L. D. Landau, E. M.Lifshits, “Mechanics of Continuous Media-Hydrodynamics”, Adison-WesleyPublishing Company, 1958):λ=P _(a)(2R _(t) /L _(pl))/(1/2)ρU _(pl) ²  (23)Where ρ is the density of liquid. The pressure, velocity and length arespecified for the case of a short plug. λ is a sophisticated function ofRe. As we are interested in plug velocity dependence on its length, theEq(23) is rewrittenU _(pl)=(4P _(a) R _(t)/ρλ_(pl))^(0.5)(1/L _(pl))^(0.5)  (24)This equation is valid for extreme case when the plug length equals totube lengthU _(o)=(4P _(a) R _(t)/ρλ_(t))^(0.5)1/(1/L _(t))^(0.5)  (25)The ratio of r.h.s. equals to the ratio of l.h.s. that yieldsU _(pl) /U _(o)=(L _(t) /L _(pl))^(0.5)(λ_(t) /λpl)^(0.5)˜(L _(t) /L_(pl))^(0.5)  (26a)FIG. 22 in (1. L. D. Landau, E. M. Lifshits, “Mechanics of ContinuousMedia-Hydrodynamics”, Adison-Wesley Publishing Company, 1958) shows thatthe friction coefficient λ(Re) decreases less than twice in the Reynoldsrange 5000 to 30000. The Eq(11b) shows that the plug velocity increasesas its length decreaseU _(pl) =U _(o)(L _(t) /L _(pl))^(0.5)  (26b)Table 1B shows the relationship between liquid plug length in thesuction tube of a typical endoscope and plug sliding velocity that canbe achieved during the DPF mode at two air pressures, 15 and 25 psig.The results of this analysis supports the inherent advantages of usingthe discontinuous modes to enhance the cleaning according to the instantinvention. This is further supported by the results on Example 19.

TABLE 1B Plug velocity as a function of plug length/total channel lengthat two pressures Plug Velocity (U_(pl)), m/s (L_(pl)/L_(t) × 100) @15psig @25 psig 1% 11.0 17.0 5% 4.9 7.6 10% 3.5 5.4 20% 2.5 3.8 30% 2.03.1 40% 1.7 2.7 50% 1.6 2.4 100% 1.1 (U₀) 1.7 (U₀)Achieving Dryout and Dewetting

It is discussed herein that it is useful for surface adjacent to therivulets or liquid entities to be substantially dry, and if alternatingflow of liquid and gas is used, it is useful for the gas flow to besufficiently long so that the internal surface substantially dries outbefore liquid flow is introduced again. Drying or de-wetting can occurby either or both of two mechanisms. One mechanism is that if theinternal surface of the passageway is sufficiently hydrophobic, when therivulet or liquid entity moves away from a particular portion of thesurface, the surface will naturally de-wet due to the absence of therivulet or liquid entity. Another mechanism is that if any of thesurface remains wet or covered by a film of liquid, the liquid canevaporate. For this purpose it may be useful for the air to be suppliedto the passageway in a condition which is dehumidified or warmer thanroom temperature or both. In such a situation, approximate times for theduration of the period of gas flow are as given here. These are for apassageway that is approximately 2 meters long, with air being suppliedat an inlet pressure of approximately 28 psig at a temperature of about4° C. For a passageway having an inside diameter of approximately 2.8 mmto 4 mm, a time period of 5 seconds to 7 seconds should be sufficient.For a passageway having an inside diameter of approximately 1 mm to 1.8mm, a time period of approximately 15 seconds should be sufficient.Shorter time periods are possible if it is not necessary that thesurface be absolutely dry, or if the surface is extremely hydrophobicsuch as Teflon® (polytetrafluoroethylene). It is also possible thatde-wetting can be aided by the flowing gas simply pushing rivulets orliquid entities to the downstream end of the passageway, withoutreplenishing them. The purpose of dewetting and drying is to prepare thesurface such that optimal detachment force may be achieved by themechanisms described in this invention. It is believed that thethickness of the residual liquid film remaining after passage of threephase contact line may be made less than the dimension of thecontaminant particles. The dryout and dewetting may be represented by astatistical distribution and it may not be possible to achieve duringevery time after passage of three phase contact line. However, it isrequired to achieve high level cleaning according to this invention.

It is further possible that the endoscope could be cleaned while theendoscope is in a position other than horizontal. For example, theposition could be vertical, such as vertical with flow in the downwarddirection. Still other orientations are also possible.

Composition of Cleaning Liquid Including Surfactant

So far we have discussed the physical parameters (gas and liquid flowrates, gas pressure, hydrophobicity of channel surface, etc.) thataffect the performance of the present cleaning method and how these canbe optimized for any channel width and length. However, the actualcomposition of the liquid cleaning medium also has an important role onthe effectiveness of the instant cleaning process.

Surfactants

It may be desirable to include one or more surfactants in the cleaningmedium. Surfactant mixtures have been found particularly useful.However, only limited classes of surfactants are useful. Based onnumerous experimentation surfactants could be divided into three classeswhen tested in endoscope channels by the flow mapping as in FIGS. 7 a to7 e.

Class I surfactants were observed to produce a wetting liquid filmwithout foaming which prevented the rivulet droplet flow (RDF),discontinuous plug flow (DPF) or discontinuous plud droplet flow (DPDF)flow regime from fully developing even at a surfactant concentration of0.05% by weight. These surfactants generally have both a low HLB(hydrophilic-lipophilic balance) and are water insoluble. Some nonionicalkyl ethoxylates where the alkyl group is linear or branched, somemembers of the PLURONIC®, REVERSE PLURONIC®, TETRONIC® and the REVERSETETRONIC® series belong to this class. However, surprisingly the HLBquoted by the manufacturer alone was not sufficient to predict theformation of a wetting film on the hydrophobic channel, e.g., TEFLON®.However, when water solubility was also very low, a wetting film usuallydeveloped. Both HLB and water solubility appear to determine asurfactant potential to form wetting films in two-phase flow. HLB<9.2and water insolubility normally lead to formation of a wetting film thatcovers the entire surface of the hydrophobic channel of endoscope at asurfactant concentration greater than about 0.05% by weight of liquidcomposition at 30 psi air pressure and low liquid flow rates. Thesesurfactants are not desirable by themselves for cleaning by the instantinvention since they do not produce surface flow entities having threephase contact line on the channel wall during flow.

Class II surfactants produce foam throughout the channel which alsoinhibits RDF (and DPDF) even at a low surfactant concentration of 0.05%by weight. These surfactants have a foaming potential as measured by aninitial Ross-Miles foam height of greater than 50 mm at 0.1%concentration and were found to produce foam that fills the entire tube(cross-section and length). The Ross Miles foam test is a well knownmeasure of the foaming potential of surfactants and is described in J.Ross and G. D. Miles, Am Soc for Testing Materials, Method D1173-53,Philadelphia Pa. 1953. Most anionic surfactants tend to fall in thisclass, except for hydrotropes which do not normally foam but also do notlower surface tension much below 50 to 55 dynes/cm. Most cationic andquaternary ammonium surfactants were also found to be fall into class IIwhen introduced into narrow channels in the presence of gas flow. Alkyl(alcohol) ethoxylates, castor-oil ethoxylates, sodium dodecyl sulfate(SDS/SLS), alkyl phenyl sulfonates, octyl and nonyl phenol ethoxylatesthat have high Ross-Miles foam index, HLB>9 and lower surface tension to25 to 35 dynes/cm are examples of this class.

Class III surfactants are those that when used individually produce theRDF and DPDF flow regimes and are desirable surfactants for cleaning anddetachment by the instant method. These surfactants normally give liquidfragments at concentrations at or above 0.05% by weight. Class IIIsurfactants normally have very low Ross-Miles Index foam height of lessthan 50 mm, preferably less 20 mm and more preferable below 5 mm orclose to zero. Many surfactants even optimal ones tend to lose theirability to produce RDF flow above 0.1% concentration either because ofthe formation of some foam or wetting films.

Several general conclusions can be drawn from our experimentalobservations with respect to surfactants and RDF/DPDF flow regimes.

Suitable surfactants for DRF/DPF tend to be mostly nonionic and variousalkoxylated surfactants although some low foaming anionic surfactantsare also suitable.

Surfactants that produce a surface tension greater than 50 dynes/cmtends to produce poor liquid fragmentation on channel wall. Although thelevel of fragmentation is better than that with water, such surfactantsonly achieve low treatment number. They normally lack detergency tosolubilize and desorb the organic soils encountered in dirty endoscopes.These types of weakly surface active surfactants include hydrotropessuch as xylene sulfonate, hexyl sulfate, octyl sulfate and ethyl hexylsulfates, or short alkyl ethoxylates and other similar nonionic orcationic agents. The liquid fragments are usually oval-shaped and do notproduce linear droplet array at their trailing ends. The advancing andreceding contact angles are high (e.g., 90 degrees or greater).

Surfactants that have surface tension less than 30 dyne/cm, especiallysurfactants that have low HLB and are water insoluble tend to produce awetting film covering the entire surface of hydrophobic channels, asmeasured by a receding contact angle of zero degrees at a surfactantconcentration in the range from about 0.05% to about 0.1% concentrationat 30 psig and typical liquid flow rate required for RDF/DPDF flow (seeexamples). Forced wetting prevails and the flow map generated can bedescribed as entirely in the “film mode” at most liquid flow rates. Thewetting film normally covers the entire surface of channel. These may ornot be associated with foam depending on other properties of thesurfactant.

Surfactants that have a low Ross-Miles foam height less than about 50mm, preferable 0 to about 5 mm and have equilibrium surface tensionbetween 33 to 50 dynes/cm can achieve RDF flow modes as shown in theflow regime maps of Examples 2-7. However, some surfactants in thisclass tend to produce some foam in the channels, especially when used athigh concentration and when used at high gas or liquid flow rates.Surfactants with surface tension of 33 to 47 dynes/cm, especially 35 to45 dynes/cm give suitable RDF regimes and provide better cleaningperformance. Mono-disperse surfactants with HLB 10-17 tend to encompassthis group of surfactants. Foam can form near the outlet of the channelwhen surface tension is about 30-34 dynes/cm.

Based on the above discussion of our experimental result, the liquidcleaning medium providing optimal flow regimes for the cleaning methodof the invention preferably should includes one or more surfactants at aconcentration that provides an equilibrium surface tension between about33 and 50 dynes/cm, preferably about 35 to about 45 dynes/cm. Thesurfactant(s) should have a low potential to generate foam as measuredby having a Ross Miles foam height measured at a surfactantconcentration of 0.1% that is less than 50 mm, preferably less than 20mm, more preferable below 5 mm, and most preferable close to zero, e.g.,less than 1 mm. The cleaning medium should not form a wetting film onthe channel surface (the interior wall of the channel) as measured by areceding contact angle greater than zero degrees. Preferably thesurfactants are water soluble and have an HLB greater than about 9.2,preferably about 10 to about 14.

Suitable surfactants for use in the cleaning mediums according to theinvention include polyethylene oxide-polypropylene oxide copolymers suchas PLURONIC® L43 and PLURONIC® L62LF, and reverse PLURONIC® 17R2, 17R4,25R2, 25R4, 31R1 sold by BASF; glycidyl ether-capped acetylenic diolethoxylates (designated “acetylinic surfactants” such as SURFYNOL® 465and 485 as described in U.S. Pat. No. 6,717,019 sold by Air Products;alcohol ethoxylates such as TERGITOL® MINFOAM 1X® AND MINFOAM 2X® soldby Dow Chemical Company and tallow alcohol ethoxylates such as SurfonicT-15; alkoxylated ether alkoxylated ether amine oxides such as AO-455and AO-405 described in U.S. Pat. No. 5,972,875 available from AirProducts and alkyldiphenyloxide disulfonates such as DOWFAX® 8390 fromDow Chemicals. Still other potentially suitable nonionic surfactantsinclude ethoxylated amides, and ethoxylated carboxylic acids, alkyl orfatty alcohol PEO-PPO surfactants and the like provided they meet thesurface tension, low foaming and non-wetting requirements

Surfactant mixtures are also suitable in the cleaning medium and havebeen found in some cases to perform better than individual surfactantsin providing RDF and DPDF regimes. Although surfactants belonging toClass III are preferred, Class I and II surfactants may be suitable asone of the components in a surfactant mixture especially when used inminor proportions. For example, the mixture may be chosen so that themixture is soluble and has an average HLB in the preferred range.However, the mixture must satisfy the non-wetting film criteriaproperties, non-foaming criteria and provide a surface tension in therequired range.

A particularly suitable surfactant mixture is a mixture of theacetylinic surfactant SURFYNOL® 485 and the alkoxylated ether amineoxide AO-455 at about 0.06% total surfactant concentration. The mixtureunexpectedly provides highly effective RDF regimes in endoscope channelscompared with the individual members of the mixture when used at thesame concentration.

It is important to note that the concentration of the surfactants andother optional ingredients will generally affect the surface activity,wetting and foaming properties of the liquid cleaning medium. Thus, forexample, a surfactant which is suitable at one concentration may not besuitable at either a lower concentration where its surface tensionlowering is insufficient or at a higher concentration where foaming orwetting (annular film formation) properties may be unsuitable. Theoptimization of the surfactant concentration to achieve optimal flowregime for cleaning is considered well within the scope of a person ofordinary skill in the art with the understanding of the basic principlesdisclosed herein.

Optional Cleaning Ingredients

Various optional ingredients can be incorporated in the liquid cleaningmedium of the invention. Preferred optional ingredients include:

pH adjusting agents: The pH of the cleaning medium should generally beabove 8.0, preferably between about 9.5 and 11.5 and more preferable10.0 to 11.0. Suitable pH adjusting agents include alkali hydroxidessuch as NaOH, KOH and sodium metasilicate, sodium carbonate and thelike.

Builders or sequestering agents: These materials complex Calcium andother di- and polyvalent metal ions in the water or soil. Examples ofsuitable builders/sequestering agents include complex phosphates such assodium tripolyphosphosphate (STP) or tetrasodium pyrophosphate (TTPP) ortheir mixtures; EDTA or other organic chelating agents; polycarboxylatesincluding citrates, and low molecular weight polyacrylates andacrylate-maleate copolymers. It has been found that some organicchelating agents may interfere with achieving the RDF mode and eachcandidate should therefore be evaluated by the methods disclosed inExample 1.

Cloud point antifoams: The cleaning solution may include additionalsurfactants that can reduce the foaming of the primary surfactants usedin the composition. For example low cloud point surfactants such asPLURONIC® L61 or L81 can be added in small concentration (e.g., 0.01 to0.025%) to decrease foaming. The concentration of the latter should beselected such that the RFD mode is maintained and that no liquid filmformation occurs in the spaces between the surface flow entities.

Dispersants: These materials promote electrostatic repulsion and preventdeposition or re-attachment of detached contaminants or bacteria tochannel surface. Suitable dispersants include polycarboxylic acid suchas for example ACCUSOL® 455N, 460N and 505N from Rohm and Haas Company,SOKALAN CP5 or CP7 from BASF and related copolymers of methacrylic acidor maleic anhydride/acid and polysulfates or sulfonates.

Solvents and hydrotropes: These materials can be used to compatibilizedthe surfactant system or help soften or solubilze soil components aslong as they do not interfere with the efficient production of optimalflow regimes for the instant cleaning method as evaluated by the methodof Example 1. Suitable hydrotropes include for example xylene sulfonatesand lower alkyl sulfate. Suitable solvents include for example glycolethers.

Oxidizing agents: As discussed above oxidizing agent suitable oxidizingagents include peroxy acids such as peracetic acid, sodium hypochloriteor sources of the same, and hydrogen peroxide or sources thereof such aspercarbonate or perborate.

It has been found that the addition of about 300 to 1000 ppm sodiumhypochlorite to the cleaning liquid is effective in the removal offibrinogen form hydrophobic endoscope channels, e.g., TEFLON®. Sodiumhypochlorite may be optionally added in the cleaning composition toavoid complications arising from blood contamination of endoscopes.

Preservatives: Preservatives known in the art can be employed to preventgrowth of organisms during storage of the cleaning composition.

In practical applications of the method, it is convenient to formulatethe liquid cleaning medium as a concentrate (2× to 20×) which is dilutedwith water before use. In order to compatibilize the various ingredientsin the concentrate, a solvent or hydrotrope may be required.

Treatment Number

It is useful to create some description of how much “sweeping” occurs ofthe internal surface of the passageway by three phase contact interfacewith sliding liquid entities or rivulets. There is limited theoreticalinformation about, for example, the transverse velocity of a meanderingrivulet. In the absence of theoretical information on this subject,high-speed photography has been utilized.

For example, from multiple photographic images taken closely together intime, it may be possible to identify the same sliding flow entity suchas a rivulet in more than one photograph, and to correlate its positionin successive photographic frames separated in time by a known timeinterval. This information in combination can provide information aboutthe velocity of meandering, such as a transverse velocity, of a rivulet,or similar information for other types of sliding flow entities. Thisknowledge can in turn be used to calculate a rate at which surface areais swept by the wet-dry interface at a three-phase contact. For slidingliquid entities other than meandering rivulets, such as for fragmentingrivulets and liquid droplet arrays, it is also possible to calculatesimilar information.

The net effect is the sweeping of the internal surface of the channel bya variety of sliding liquid entities including meandering rivulets,sub-rivulets, rivulet fragments, linear droplets arrays and individualdroplets of various sizes all in contact with the surface of thechannel. Each of these entities has an associated three-phasegas/liquid/solid contact interface and meniscus. The overall effect ofthe sliding of these surface flow entities is the sweeping of thesurface of the channel by multiple moving three-phase contact interfacesand menisci.

A criterion of some significance would be the situation in which theamount of area swept by the motion of sliding liquid entities is equalto the internal surface of the passageway. In this situation, if therewere no duplication of sweeping any particular points, each point on theinternal surface of the passageway would be swept once and thereforewould experience at least one cleaning action. Of course, given therandom and statistical nature of the processes described herein, it ispossible that some points could be swept more than once by the motion ofa sliding liquid entity while some other points might not be not sweptat all. Therefore, it may be desirable for cleaning to be performed suchthat the Treatment Number is greater than 1. First of all, having aTreatment Number somewhat larger than 1 would make it likely that everyindividual point is swept at least once, even if some points are sweptmore than once. Furthermore, having a Treatment Number sufficientlylarger than 1 could make it likely that most points or all points areswept several times. This would further improve the quality of thecleaning. Of course, it is possible that there might be contaminants forwhich one sweep by a sliding liquid entity is not sufficient to removethe contaminant, but several such sweeps might accomplish the removal.

Therefore, for example, cleaning might be performed such that cleaningaccomplishes a Treatment Number of at least 5, or at least 10, or atleast 25.

It is possible that cleaning by the described methods can be performedfor a sufficient length of time so as to achieve a log-reduction ofabout 5 to 6 in the number of organisms and organic soils, includingproteins, from long and narrow internal passageways.

The treatment number may be different at different places along thelength of the endoscope channel. The treatment number also may bedifferent locally at a given cross-section of an endoscope channel, suchas at different places around the perimeter of a particularcross-section of the endoscope channel. For example, cleaning conditionsmay be chosen such that a minimum value of treatment number is achievedat all locations, and larger values are achieved at some locations.

A quantitative measure of the extent to which the surface of the channelis swept by surface flow entities is provided by a parameter designatedas a Treatment Number, NT, defined as the total area that is swept byall the surface flow entities divided by the total internal surface areaof the channel. Treatment number equals one means that the entirechannel is swept one time by surface flow entity. The Treatment Numbercan be computed from high speed photography of sample areas of specificdimensions (e.g., 400 μm by 300 μm) taken at various positions on theinternal surface of the channel at different locations along its lengthby the following procedure. The determination of Treatment Number can becombined with the hydrodynamic flow mapping outlined above and describedin detail below.

The total area swept in a fixed time t_(cl) (e.g., 300 sec) by aparticular surface flow entity (SFE), e.g., a drop or cylindrical body,of diameter d_(SFE,i) is:A _(SFE,i) =d _(SFE,i) U _(SFE,i) t _(cl)  (12)

where U_(SFE,i) is the sliding velocity of the i_(th) SFE, i.e., therate at which the three-phase contact line at the leading edge of therivulet fragment moves over the surface.

The total area swept during t_(cl) for all the types of SFE that appearwithin a sample volume element (e.g., the field of view), includingthose SFE that enter and leave during the total observation time is:Total Area Swept by Rivulet Fragments=Σ_(i) d _(SFE,i) U _(SFE,i) t_(cl)  (13)

where the sum is taken over all rivulet fragments.

Eq. 2 can be generalized for all types of surface flow entities(meandering rivulets, cylindrical bodies, linear droplet arrays, largedrops, small drops, etc.) asTotal Area Swept by All Surface Flow Entities=A _(cl,Tot) =t_(cl)Σ_(k)Σ_(i) d _(k,i) U _(k,i)  (14)

where d_(k,i) is the diameter of the i_(th) SFE of the “k_(th)” type,e.g., discrete droplet, having an average sliding velocity U_(k,i).

The average sliding velocity of each surface flow entity can be measuredby observing the movement of the flow entity in the axial direction orfor meandering rivulets both axial and radial direction over time.Because of their rapid movement under the influence of gas flow, we haveutilized multi-exposure time-lapse photography in which the camerashutter is allowed to remain open and exposure is controlled by a strobelight. By measuring the change in position of the moving three-phasecontact line over time, the velocity of each SFE, can be determined anda distribution function of sliding velocity computed for each type offlow entity.

The Treatment number, N^(j) _(T), is defined as the total area swept byall SFE divided by the total area of the channel, A_(C) at theparticular position being viewed, i.e., the “j_(th)” section or volumeelement of the channel along its length. For channels that are circularcylinders, A^(j) _(C) is equal to πDI where πD is the channel perimeter,and I is the length of the visual area being viewed in axial direction.The treatment number at the “j_(th)” section (volume lement) is thengiven by:N ^(j) _(T) =A ^(j) _(cl,Tot) /A ^(j) _(C)=(t _(cl) /πD ² I^(j))Σ_(k)Σ_(i) d ^(j) _(k,i) U ^(j) _(k,l)  (15)

where the superscript “J” refers to the “j_(th)” viewing area.

The terms in Eq. 4 can be separated into different flow entities andfurther subdivided into discrete size ranges. The average slidingvelocity of each type of flow entity falling into each size range canthen be computed from the measured average velocities or a velocitydistribution function.

The inspection of a large number images revealed that the distributionof SFE (Surface Flow Entities) within any image is non uniform and onlya relatively small strip of available area is cleaned at any instant oftime. However, the time of residence of a particular SFE within thevisual area is much less than a second and the number and type of SFEobserved within the viewing area will change more than 300 times, if thecleaning time is for example 300 sec. Since the location of specificentities are different for different moments of time, a rather uniformtreatment is achieved provided a sufficient time is allowed for cleaningand the treatment number is sufficiently large. On the other hand, theshorter the cleaning time, the larger will be the manifestation of largenon-uniformities in the momentary distribution of SFE.

When the Treatment Number is ˜1, the treatment uniformity is low.Although the area of the channel swept by SFE is equal to the geometricarea of the channel, large regions of the channel remain untreated.However, when N^(j) _(T) exceeds 30, and preferably exceeds 50, thetreatment of the particular section being viewed is sufficiently uniformsuch that all areas of the section are cleaned. When the treatmentnumber reaches about 100 or more, a very high degree of uniformity interms of fraction of total area swept by three-phase contact lines isobserved.

Based on the above analysis, the Treatment number N^(j) _(T) atsubstantially all positions along the length of the tube (from inlet tooutlet) should be greater than 10, preferably at least about 30, morepreferably between and most preferably greater than about 50. Be theterm substantially all positions along the length of the tube is meantat least about 75% of length of the tube, preferably greater than 80% ofthe tube length and most preferably greater than 95% of the tube length.

The instant method is in fact capable of routinely achieving very hightreatment numbers of 100 or more and under some conditions 300 to 1000.These high treatment numbers achieve very high log reduction, e.g. pLog6 in contaminant microorganisms.

Inspection of Eq. 4, indicates that treatment number depends upon thetotal number of surface flow entities formed over the course of thecleaning operation and their sliding velocities. Operationally, thesevariables are controlled by the liquid and gas flow rates and byinterfacial properties and other properties such as viscosity of theliquid cleaning medium.

As the liquid flow rate increases the amount and type of SFE increases.This leads to an increase in Treatment Number with increasing liquidflow rate which is well documented experimentally by the analysis ofphotomicrographic images taken under various conditions.

Similarly, an increase in gas flow rate increases the number of surfaceflow entities and their sliding velocity since it is the drag forceprovided by the flowing gas which induces fragmentation and rapidsliding in the first place.

In a further embodiment of the instant cleaning method utilizing the RDFflow regime either or both the rivulet flows of liquid cleaning mediumor the flow of gas are pulsed during the cleaning cycle which has beenfound to aid detachment of contaminants in some cases.

Endoscope Structure

There are a variety of endoscope designs for particular surgical ordiagnostic procedures, and even endoscopes for the same surgicalprocedure can have design differences among different models produced bydifferent manufacturers. Typical features of an endoscope areillustrated in FIG. 12. As a general feature, an endoscope may have adistal end 100 which goes inside the patient. Some distance back fromthe distal end 100 there may be a control handle 90 at which certaincontrols can be operated and access may be obtained to the channelsinside the endoscope. Between the distal end 100 and the control handle90, the endoscope is flexible. Continuing further back from the controlhandle 90, there may be another flexible length, umbilical cable 80,which ends at an umbilical end 70.

For any of the channels, the lengths of the various channels maytypically be the same for all of the channels, because the lengths ofall of the channels are related to the length of the endoscope itself.The portion of the endoscope from the control handle to the distal end100 may have a maximum length of approximately 2 to 2.6 m. The umbilicalportion of the endoscope (between the control handle 90 and theumbilical end 70) may have a length of approximately 1.4 m.

An endoscope may comprise an air channel 132 and a water channel 131.These channels 131, 132 may be similar to each other or even identicalto each other. These may be some of the smaller-diameter channels withinthe endoscope. For example, the inside diameter of the air channel 132and the water channel 131 may be relatively small, approximately 1 mm.Air channel 132 and water channel 131 may extend the entire length ofthe endoscope, from the umbilical end 70 to the distal end 100, withaccess points at the control handle 90. Air channel 132 and waterchannel 131 may come together at the distal end 100 of the endoscope andmay discharge at the distal end 100 through a common orifice (orair-water nozzle) 133. The common orifice 133 may have an insidediameter that is smaller than the inside diameter of the air channel 132or the water channel 131.

An endoscope may comprise a suction channel 109A which may also serve asa biopsy channel. The internal diameter of such channel 109A can varyover a significant range, such as from 1.2 mm to 6.0 mm depending on thepurpose and design of that channel and that endoscope.

Some endoscopes may further comprise a forward water jet or irrigationchannel. This channel may have an inside diameter which is also in therange of 1 mm. It is possible that the forward water jet or irrigationchannel may extend from the control handle 90 to the distal end 100without having another channel segment between the control handle 90 andthe umbilical end 70. Alternatively, it is possible that the water jetor irrigation channel may extend from the umbilical end 70 all the wayto the distal end 100 without having an access point at the controlhandle 90.

For any of the channels that extend from the control handle 90 to thedistal end 100 and also from the control handle 90 to the umbilical end70, it is possible that the inside diameter of the segment from thecontrol handle 90 to the distal end 100 may be different from the insidediameter of the segment from the control handle 90 to the umbilical end70. Typically, if there is a difference, the inside diameter of thesegment from the control handle 90 to the distal end 100 may be smallerthan the inside diameter of the segment from the control handle 90 tothe umbilical end 70.

FIG. 12 shows details at the control handle of a typical endoscope. InFIG. 12 there is shown a suction cylinder well 103 having connections tothe suction channel. At this cylinder well 103 there is one connection105 heading toward the distal end 100, and the other connection 104heading toward the umbilical end 70.

In FIG. 12 there are shown an air/water cylinder well 126 that containsconnections to the air channel and connections to the water channel,both meeting at a common air/water cylinder well 126. Thus, thiscylinder well 126 has four ports. Port 128 is for the water channelheading toward the distal end 100 of the endoscope, and port 127 is forthe water channel heading toward the umbilical end 70 of the endoscope.Port 130 is for the air channel heading toward the distal end 100 of theendoscope, and port 129 is for the air channel heading toward theumbilical end 70 of the endoscope.

A suction/biopsy channel 102, may extend from the suction nipple 101located at the umbilical end 70, to the suction control cylinder well103 located at the control handle 90, and may further extend throughchannel 107 from the suction control cylinder well 103, to meet withchannel 109 which is connected with the biopsy insert port 108. Thesuction/biopsy channel is then continued with a plastic tubing 109A tomeet with the discharge port 108, located at the distal end. Asuction/biopsy control cylinder well 103, is a metal housing used toaccommodate a suction control valve during application where an inletport 104, and an outlet port 105, are included to connect with theplastic tubing 107 and the plastic tubing 102.

The air channel 124 may extend from the air/water port 121, located atthe umbilical plug 70, to the air/water cylinder well 126, located atthe control handle 90, and may further comprise channel 132 extendingfrom the air/water cylinder well 126, to the air/water nozzle 133,located at the distal end of the endoscope. The water channel 123 mayextend from the air/water port 121, located at the umbilical end 70, tothe air/water cylinder well 126, located at the control handle 90, andmay further comprise channel 131 extending from the air/water cylinderwell 126 to the air/water nozzle 133, located at the distal end 100 ofthe endoscope. The various channels may be tubing made of polymer suchas polytetrafluoroethylene.

In many types of endoscopes, the air/water nozzle 133, located at thedistal end 100 is the point where the air channel 124 and water channel123 meet. The inside diameter of nozzle 133 may be smaller than theinside diameter of the air channel 124 or the water channel 123 itself.

An endoscope may comprise a forward water jet (or irrigation) channel142. This channel 142 may extend from the forward water jet port 141located at the control handle 90 or at the umbilical plug 70, to thedischarge port 143 located at the distal end 100.

Some endoscopes may contain an elevator channel 111, which is a tubehaving a wire inside it which is used to steer the tip of the endoscope.The elevator channel 111 may extend from the elevator wire channelcleaning port 110 located at the control handle 90, to the distal end100. Thus, the elevator wire channel may be shorter than some otherchannels that may extend the entire length of the endoscope. A wire 112may be installed inside the elevator wire channel 111. One end of thewire 112 is attached to an elevator raiser 113 which is hinged near thesuction discharge port 108 at the distal end. The other end of the wire112 may be attached to a control knob mechanism at the control handle 90which starts from the elevator wire channel cleaning port 110. Thedimensional space between the elevator wire and the tubing whichsurrounds the elevator wire may be approximately 0.18 mm. Typically theelevator channel is pressure-tested to a higher pressure than any otherpassageway of the endoscope.

Among various endoscopes, typical lengths and inside diameters ofcertain channels can be tabulated, or at least ranges of thesedimensions can be tabulated. These are summarized in Table 2.

TABLE 2 Channels - Umbilical to Control Handle: Air & Water ChannelsSuction Channel Water Channel** Internal Internal Internal DiameterLength Diameter Length Diameter Length 1.4 to 1.4 m 1.2 to 5.0 mm 1.4 m1.2 to 1.4 mm 1.4 m 1.6 mm Channels - Control Handle to Distal End:Forward Water Jet/ Air & Water Elevator Wire/ Channels Suction ChannelIrrigation Channels Internal Internal Internal Diameter Length DiameterLength Diameter Length 1.0 mm 2.0 to 1.2 to 5.0 mm 2.0 to ≧1.0 mm 2.5 m(smallest) 2.6 m 2.6 m (FWJ)  <0.8 mm (EW) ≧1.0 mm (Irrigation)

Endoscopes may further comprise still other components such as fiberoptics and electronics, which are omitted here for clarity ofillustration.

Endoscope Cleaning Apparatus Circuits

An endoscope cleaning apparatus 50 may comprise a variety of fluid flowcircuits and other apparatus. These are illustrated in FIGS. 13 a-13 d.FIG. 13 a is an overall system schematic. FIGS. 13 b, 13 c and 13 dillustrate portions of FIG. 13 a in more detail. For example, FIGS. 13b, 13 c and 13 d include valves that are omitted from FIG. 13 a for sakeof clarity.

i) Air Circuit: The air-flow circuit design 1 may include an air inlet1G from an outside source or compressor, air distribution branches 1Eand 1F to perform pressure leak test of Scopes A and B, to inject airinto distribution manifold A (8), distribution manifold B (9) andelevator manifold (10) via lines 1A, 1D and 1C for rivulet-droplet flowcleaning and rinsing and also for drying the internal channels. The airmay be dehumidified or less-than-fully-humid. As illustrated, the airpasses through a dehumidifier 1I before entering the rest of theapparatus 50. It is also possible, that air may pass through a heater 1Jbefore being used for various purposes. Heating of air can be expectedto further reduce its humidity. Air from this air circuit may also beused for purging water lines 1H and disinfectant lines 1B of theapparatus 50.

ii) Water Circuit: The water circuit design 2 may include a heated waterinlet 21 from outside, supplies water to rinse all the endoscopeinternal channels through the distribution manifold A (8), distributionmanifold B (9) and elevator manifold (10) via lines 2A, 2C and 2D, aswell as to rinse the external surfaces of endoscopes through the basinvia line 1E. This circuit also provides water to perform channel patencymeasurements for Scopes A and B via lines 6 and 12, to rinse thedisinfectant circuit via line 2B, and the cleaner circuit via line 2Gand to mix it with the concentrated cleaning solution for final dilutionvia line 2H.

iii) Cleaner Circuit: This circuit design 3 may include a concentratedcleaning solution inlet 3F from the bottle, a water source for mixingwith concentrated cleaning solution (2H) and a water source for rinsingthe cleaner circuit (2G). The cleaner circuit provides cleaning solutionto the distribution manifold A (8), distribution manifold B (9) andelevator manifold (10) via lines 3A, 3B and 3D to performrivulet-droplet flow cleaning of the internal channels and providescleaning solution to the basin via line 3C to perform external cleaningof endoscope surfaces. This circuit is also used to supply peraceticacid (PAA) to the basin via line 3E during the self-disinfection cycle.

iv) Disinfectant Circuit: The high-level disinfection circuit design 7includes: a storage tank and a recirculation loop (7A and 4E) with anin-line heater 4F to maintain the disinfectant at 35° C. This circuitsupplies disinfectant to the basin to achieve complete immersion for 5minutes at 35° C. The internal channels are flooded with thedisinfectant during the disinfection cycle from the basin throughdistribution manifold A (8), distribution manifold B (9) and elevatormanifold (10) via lines 4A, 4B and 4D. During disinfection, the sprayarm and eductors direct the disinfectant to endoscope surfaces and coverthe surfaces of the basin, including the lid of the apparatus. Thedisinfectant circuit design simultaneously supplies disinfectant to thebasin and then recirculates it through the distribution manifolds andthe eductors for high-level disinfection of internal channels andexternal surfaces, respectively. This circuit also maintains thetemperature of disinfectant in the reservoir by recirculating it througha heater 4F.

v) Alcohol Circuit: The alcohol circuit 5 supplies alcohol todistribution manifold A (8), distribution manifold B (9) and elevatormanifold (10) via lines 5A, 5B and 5C before the final drying step withair to facilitate drying.

vi) Distribution Manifold Circuits: Distribution manifold A (8) anddistribution manifold B (9) are used to generate rivulet-droplet flowand to supply different fluids to the internal channels of twoendoscopes, A & B. Each distribution manifold has five inlet ports (air(1A, 1D), water (2A, 2C), cleaning solution (3A, 3B), alcohol (5A, 5B)and basin (4A, 4B)) and five outlet ports (air (8A, 9A), water (8B, 9B),suction (8C, 9C), biopsy (8D, 9D) and irrigation (8E, 9E) channels).Elevator manifold 10 is also used to generate rivulet-droplet flow andhas the same five inlet ports (1C, 2D, 3D, 5C and 4D) but only twooutlet ports, one for the elevator wire channel of Scope A (10A) and theother for the elevator wire channels of Scope B (10B). FIG. 13 b shows aschematic of Manifold A (8) in detail. The air (1A), water (2A), cleaner(3A), basin (4A) and alcohol (5A) inlets to manifold A (8) arecontrolled by valves 8F, 8G, 8H, 8I and 8J, respectively. The outletfrom the manifold to air port (8A), water port (8B), suction port (8C),biopsy port (8D) and water irrigation port (8E) are controlled by valves8K, 8L, 8M, 8N and 8O, respectively.

vii) Basin Circuit: This circuit design shown in FIG. 13 d providescleaning solution 3C, water 2E and disinfectant 7A through eductors 4Gusing circulation pump 4H and valve 4I and spray arm 4J usingcirculation pump 4H and valve 4K to clean, rinse and disinfect theexternal surfaces of two endoscopes. For simplicity, in FIG. 13 d onlyone eductor (4G) is illustrated. The basin 4 circuit circulatesdisinfectant through the endoscope internal channels using distributionmanifold A (8), distribution manifold B (9) and elevator manifold (10)via lines 4A, 4B and 4D, and discharges the contents of the basin to anoutside drain 4C. The temperature of disinfectant 7 in the basin 4 ismaintained by circulating it through the disinfectant bottle via aheater 4F and lines 4E and 7A. The vent 4L is also provided in the basin4 to prevent any pressure build up inside the basin 4. This circuit alsosupplies sterilant such as peracetic acid (PAA) (11) sterilant from thePAA bottle through the cleaner lines 3E and 3C to the basin 4 to executethe self-disinfection cycle.

Patency Testing. FIG. 13 c shows a schematic of the patency testingcircuit for Scope A in detail. Water (6) from the water circuit (2) ispassed at a fixed pressure (pressure monitored by pressure sensor 6G)through a water regulator 6F and one of the following five channels: air(6A), water (6B), suction (6C), water irrigation (6D), and biopsy (6E),by their respective valves. Likewise, for Scope B, water (12) from thewater circuit (2) is passed through one of the following five channels:air (12A), water (12B), suction (12C), water irrigation (12D) and biopsy(12E), by their respective valves. The water flowrate through a channelis measured by water flowmeter (6H). The water injection to the air(6A), water (6B), suction (6C), water irrigation (6D) and biopsy (6E)channels is controlled by valves 6I, 6J, 6K, 6L and 6M, respectively.

Reprocessing Cycle for a Single Channel

During reprocessing, the apparatus 50 (FIG. 13 a) may supply all or anysubset of the following fluids to an endoscope at appropriate times, ormay perform all or any subset of the following actions. The reprocessingcycle for any given channel may include the following steps: i)pre-cleaning, ii) leak and patency testing, iii) rivulet-droplet flowcleaning, iv) rinsing, v) disinfection, vi) rinsing, vii) alcoholflushing, and viii) air drying. This sequence of events is furtherillustrated in FIG. 14.

In preparation for reprocessing of an endoscope, it is possible thatupon completion of an endoscopic procedure, channels of the endoscopecan be filled with liquid or wetted in some manner so that debris thatmay have been deposited during the endoscopic procedure remains wetduring the time between the endoscopic procedure and the reprocessing.This can help to maintain the debris in a condition such that it can beremoved more easily.

i) Pre-Cleaning

The pre-cleaning step may include a pulsed rivulet-droplet flow with thecleaning solution through the endoscope channel to remove gross patientmaterial from the channel. A mixture of water from water circuit 2 andcleaning solution from cleaner circuit 3 may be passed through thechannel for a period of time, followed by an air pulse from air circuit1 for a period of time, and this process may be repeated several timesthroughout this step. It is also possible that toward the end of thispre-cleaning step, there can be a flushing of the channel with a flowentirely of liquid such as water using water circuit 2.

ii) Leak and Patency Testing

In a leak test, air from air circuit 1 at a modest pressure such asapproximately 3 psig may be applied to the endoscope sheath, and thedecay of pressure as a function of time may be monitored by a pressuresensor. If the pressure decay is outside the acceptable range, then theendoscope fails the leak test. In a patency/obstruction testing of anendoscope internal channel, a flow of water from water circuit 2 atknown constant temperature and pressure may be applied to the channeland then the flow rate in the channel may be monitored with a precisionflow meter/sensor. This patency-testing system may determine the channelobstruction or blockage in either or both of two ways: (1) by comparingthe flow rates obtained against baseline values of that particularchannel of that particular endoscope (new condition) which may be storedin the database of the apparatus, and (2) by comparing the measured flowrate measured against a default value for a channel having the samediameter and length whose values are also stored in the database of theapparatus.

iii) Rivulet-Droplet Flow Cleaning

In this step, a channel may be cleaned for a period of time using, atleast some of the time, the rivulet-droplet flow regime. In therivulet-droplet flow cleaning, warm air from air circuit 1 at knownpressure and warm cleaning solution from cleaner circuit 3 at known flowrate may be caused to flow through the channel. The flowrates may bechosen based on the internal diameter and length of the channel so as toform rivulet droplet flow so as to detach contaminants from the surfaceof the channel. At the end of this rivulet-droplet flow cleaning, thechannel may be purged with air from air circuit 1 for a short period oftime to remove cleaning solution from the channel.

iv) Rinsing

A special rinsing step may be performed to remove detached contaminantsfrom the endoscope internal channel or to remove cleaning solution fromthe channel. This rinsing step may be performed using substantially purewater. This rinsing step may include two sub-steps: pulsedrivulet-droplet flow rinsing and continuous water rinsing. In the pulsedrivulet-droplet flow rinsing, water from water circuit 2 may be passedthrough the channel for a period of time followed by an air pulse fromair circuit 1 for a period of time, and this process may be repeatedseveral times. In the continuous water rinsing, water from water circuit2 may be passed through the channel. At the end of rinsing, the channelmay be purged with air from air circuit 1 for a short period of time toremove water from the channel.

v) Disinfection

High-level disinfection may be performed using an FDA approveddisinfectant (for example, glutaraldehyde at 35° C. for 5 minutes orperacetic acid (PAA)). In this step, the disinfectant from disinfectantcircuit 7 may be circulated from the basin 4 through the internalchannel while the endoscope is completely immersed in the disinfectantinside the basin 4. At the end of disinfection step, the channel may bepurged with air from air circuit 1 for a short period of time to removedisinfectant from the channel.

\vi) Rinsing

In this step, water from water circuit 2 may be passed through thechannel to remove traces of disinfectant. At the end of rinsing, thechannel may be purged with air from air circuit 1 for a short period oftime to remove water from the channel.

vii) Alcohol Flushing

In this step, alcohol from alcohol circuit 5 may be passed through thechannel for a period of time. The alcohol may be or may compriseethanol. This may serve the purpose of facilitating drying because thealcohol may evaporate more easily than water.

viii) Air Dying

In this step, the channel may be purged with warm air from air circuit 1to dry the endoscope internal channels.

Separate from the described cycle for cleaning internal channels of anendoscope, the apparatus may also provide a special cycle for performingself-disinfection where a disinfectant is used to disinfect the fluidlines within the endoscope reprocessing apparatus itself, such as toremove possible biofilm. Self-disinfection may, for example, beperformed on a periodic basis such as weekly. The substance used forself-disinfection may, for example, be peracetic acid.

The apparatus 50 (FIG. 13 a) may also provide a special cycle for watersampling where the basin is filled with water and a water sample istaken through a special port.

Cleaning Two Endoscopes at the Same Time Non-identically

For sake of efficiency or convenience, it may be desirable for a singleapparatus to be able to clean two endoscopes at the same time orapproximately at the same time. A sequence of events for accomplishingthis is illustrated in FIG. 15.

The two endoscopes may be either identical to each other or differentfrom each other. Even if the endoscopes are identical to each other, atany given instant of time, the cleaning operation being performed on oneendoscope (or a particular passageway of that endoscope) may or may notbe identical to the cleaning operation being performed on the otherendoscope (or a particular passageway of that endoscope).

Certain passageways may have greater needs than other passageways. Thisneed may be expressed in terms of consumption of electrical power, or interms of consumption of compressed air, or consumption of still otherutilities. Any utility such as electricity or compressed air or otherutility may be in limited supply, or may be such that it is desirable tokeep its maximum demand below a certain limit, or to minimize suchmagnitude of maximum demand. For example, it is the maximuminstantaneous demand that determines electrical supply requirements.Similarly, in regard to compressed air consumption, although storage ofcompressed air is possible to some degree, still in general the maximuminstantaneous consumption of compressed air is likely to significantlyinfluence the necessary capacity of the air compressor (and therefore tosome extent the electrical power consumption of the apparatus).

FIG. 15 a illustrates a possible sequence of events for cleaning twoendoscopes at least approximately simultaneously but not with theidentical sequence of events. For sake of illustration, FIG. 15 a usesthe example of a Scope A and a Scope B. As illustrated in FIG. 15, it ispossible to schedule operations during simultaneous processing of twoendoscopes, such that cleaning of a relativelylow-air-flowrate-consumption passageway is performed in one endoscope atthe same time that cleaning of a relativelylarger-air-flowrate-consumption passageway is performed on the otherendoscope. At a later time, the operations can be reversed. In this way,it is possible to clean two endoscopes simultaneously, and yet the peakdemand for consumption of compressed air can be kept at less than twicethe air consumption of the largest-air-consumption passageway.

It may be desirable to minimize the peak rate of consumption ofcompressed air not only for reasons of minimizing the peak rate ofconsumption of electrical energy, but also for other reasons such ascapital cost of an air compressor, peak noise generation, overall sizeor weight of the equipment, and other reasons.

Of course as described elsewhere herein, the conditions for achievinggood cleaning of one geometric passageway may be different from theconditions for achieving good cleaning of one geometric passageway.These conditions may differ in liquid/gas ratio, or may differ in timingand scheduling, or both. Equipment which cleans two endoscopessimultaneously, or even which cleans different passageways within asingle endoscope simultaneously, may be operated so as to supply toindividual passageways the conditions which are appropriate to thatparticular passageway.

If the apparatus is capable of cleaning more than one different designor model or brand of endoscope, it may be capable of cleaning more thanone different design or model or brand of endoscope simultaneously. Inthat case, the apparatus may be capable of being programmed to identifywhich type of endoscope is being cleaned at a particular station withinthe apparatus, or the apparatus may be capable of recognizing what typeof endoscope is present at a particular station. Furthermore, theapparatus may be capable of delivering air appropriately for eachendoscope.

FIG. 15 b illustrates various details of types of flow inputs that couldbe performed during cleaning. Such flow inputs could also be appliedduring pre-cleaning or during rinsing.

Reprocessing Cycle for Cleaning Two Endoscopes ApproximatelySimultaneously:

The reprocessing cycle for two endoscopes may include the followingsteps as described elsewhere herein for a single endoscope: i)pre-cleaning, ii) leak and patency testing, iii) rivulet-droplet flowcleaning, iv) rinsing, v) disinfection, vi) rinsing, vii) alcoholflushing, and viii) air drying. This sequence of events is furtherillustrated in FIG. 15. During reprocessing, the apparatus 50 (FIG. 13a) may perform all or any subset of the following steps:

i) Pre-Cleaning:

The pre-cleaning step may include a pulsed rivulet-droplet flow with thecleaning solution through the endoscope channel to remove gross patientmaterial from the channel. A mixture of water from water circuit 2 andcleaning solution from cleaner circuit 3 may be passed through thechannel for a period of time, followed by an air pulse from air circuit1 for a period of time, and this process may be repeated several timesthroughout this step. It is also possible that toward the end of thispre-cleaning step, there can be a flushing of the channel with a flowentirely of liquid such as water using water circuit 2.

ii) Leak and Patency Testing:

The leak test is performed on Scope A while the patency test isperformed on Scope B. This is followed by patency test on Scope A andleak test on Scope B. In the leak test, 3 psi air from air circuit 1 isapplied to the endoscope sheath and the pressure decay is monitored by apressure sensor as a function of time. If the pressure decay is morethan the acceptable range then the endoscope fails the leak test. In thepatency/obstruction testing of endoscope internal channels, a flow ofwater from water circuit 2 at known constant temperature and pressure isapplied to each channel separately and then the flow rate in the channelis monitored with a precise flow meter/sensor. This patency-testingsystem determines the channel obstruction or blockage in two ways: 1) bycomparing the flow rates obtained with baseline values of the sameendoscope (new condition) stored in the database of the apparatus, and2) by comparing the flow rates measured with a default value of channelsof the same diameter and length whose values are also stored in thedatabase of the apparatus (for repaired endoscopes). In our apparatus,we include means to separate all endoscope channels from each other sothat the patency of each channel can be tested without any interferencefrom the other channels.

iii) Rivulet-Droplet Flow Cleaning:

In our apparatus, one large channel (for example, suction, biopsy) fromScope A and one small channel (for example, air, water) from Scope B maybe cleaned simultaneously for a period of time using distributionmanifold A (8) and distribution manifold B (9), respectively. This maybe followed by cleaning one small channel from Scope A and one largechannel from Scope B for a period of time, again using distributionmanifold A (8) and distribution manifold B (9), respectively. Thissequence may be continued until all the channels are cleaned. Theelevator wire channel may be cleaned continuously throughout the wholerivulet-droplet flow cleaning cycle using elevator manifold (10). In therivulet-droplet flow cleaning, warm air from air circuit 1 at knownpressure and warm cleaning solution from cleaner circuit 3 at known flowrate may be applied through each channel based on the internal diameterand length of the channel to detach contaminants from the surface of thechannel. At the end of rivulet-droplet flow cleaning, all the channelsmay be purged with air from air circuit 1 for a short period of time toremove cleaning solution from the endoscope internal channels.

iv) Rinsing:

A special rinsing step may be performed to remove detached contaminantsfrom the endoscope internal channel or to remove cleaning solution fromthe channel. This rinsing step may be performed using substantially purewater. This rinsing step may include two sub-steps: pulsedrivulet-droplet flow rinsing and continuous water rinsing. In the pulsedrivulet-droplet flow rinsing, water from water circuit 2 may be passedthrough Scopes A and B via distribution manifold A (8) and distributionmanifold B (9), respectively, for a period of time followed by an airpulse from air circuit 1 for a period of time and this process isrepeated several times. In the continuous water rinsing, water fromwater circuit 2 may be passed through all the channels of Scopes A and Bat the same time. At the end of rinsing, all the channels may be purgedwith air from air circuit 1 for a short period of time to remove waterfrom the endoscope internal channels.

v) Disinfection:

High-level disinfection may be performed using an FDA approveddisinfectant (glutaraldehyde at 35° C. for 5 minutes or peracetic acid(PAA)). In this step, the disinfectant from disinfectant circuit 7 maybe circulated from the basin 4 through the internal channels of Scopes Aand B using distribution manifold A (8) and distribution manifold B (9),respectively while the two scopes are completely immersed in thedisinfectant inside the basin 4. At the end of disinfection step, allthe channels of Scopes A and B may be purged with air from air circuit 1for a short period of time to remove disinfectant from the endoscopeinternal channels.

vi) Rinsing:

In this step, water from water circuit 2 may be passed through all thechannels of Scopes A and B at the same time to remove traces ofdisinfectant. At the end of rinsing, all the channels may be purged withair from air circuit 1 for a short period of time to remove water fromthe endoscope internal channels.

vii) Alcohol Flushing:

In this step, alcohol from alcohol circuit may be passed through all thechannels of Scopes A and B using distribution manifold A (8) anddistribution manifold B (9), respectively for a period of time. Thealcohol may be or may comprise ethanol. This may serve the purpose offacilitating drying because the alcohol may evaporate more easily thanwater.

viii) Air Dying:

In this step, all the channels of Scopes A and B are purged with warmair from air circuit 1 using distribution manifold A (8) anddistribution manifold B (9) to dry the endoscope internal channels.

As described elsewhere herein, the apparatus may also include specialcycles for water sampling where the basin is filled with water and awater sample is taken through a special port. The apparatus may alsoinclude special cycles for performing self-disinfection where a seconddisinfectant is used to disinfect all the fluid lines of the endoscopecleaning apparatus.

Apparatus Supplying Heated or Dehumidified Air

It is described elsewhere herein that a liquid entity travelling over asolid surface which is dry or hydrophobic is believed to help causedetachment of contaminants, by virtue of the moving three-phase contactinterface. One way of promoting this situation is to have an appropriaterelationship of hydrophobicity between the liquid and the solid surface.Another factor promoting this situation is to help cause evaporation ofliquid, such as water, which is used for cleaning. Evaporation may bepromoted if the gas which is supplied to the flow is less than fullyhumid. If air is the gas used for the gas flow, this condition may beachieved by dehumidifying the air before it is supplied to thepassageway. Appropriate dehumidification means are known in the art.Alternatively, this may be achieved by heating room-temperature air to aslightly elevated temperature. Even if the air were fully humid ornearly fully humid when it was at room temperature, when it becamewarmer it would be less than fully humid and therefore would be capableof promoting some evaporation of liquid. Of course, it is also possibleto both dehumidify and heat the air or other gas which is supplied ofthe passageway.

Of course, it is also possible that the liquid supplied to thepassageway can be warm or hot. In general, heating of either the liquidor the gas or both may also help cleaning by speeding up diffusionprocesses, by denaturing protein, by helping to soften of debris orcontaminants, and by other mechanisms.

An air heater element 1J is illustrated in the air circuit in FIG. 13 a.Heating of the liquid can be accomplished internally in the apparatus,by a liquid heater (similar to air heater element 1J but not shown) or,perhaps more likely, warm or hot water from an external source can betaken into the apparatus, possibly with temperature control eitherexternal to the apparatus or internal to the apparatus.

For example, flow of heated gas may be provided, in the absence ofliquid being supplied, for a duration of approximately 5 seconds to 15seconds depending on passageway inside diameter, passageway length,humidity, temperature and possibly other factors. With a gas supplypressure of about 30 psig, a duration of 5 to 15 seconds flow of gas (inthe absence of liquid being supplied) may be appropriate for drying orde-wetting the air/water channel. A duration of 5 to 7 seconds may beappropriate for drying or de-wetting a suction channel.

Furthermore, it may be appreciated that this process of drying out andre-wetting may be repeated a number of times. This can insure that evenif a particular patch of surface does not experience re-wetting during aparticular plug flow or a particular experience of rivulet droplet flow,it may experience re-wetting during a subsequent plug flow or asubsequent experience of rivulet droplet flow. Furthermore, any patch ofsurface may experience drying out and re-wetting a number of times, toinsure good cleaning. This is described by the Treatment Number asdiscussed elsewhere herein. This differs from the situation in which itis possible that a passageway to be cleaned might possibly start thecleaning process in an initially dry condition and therefore, as sort ofa trivial example, would by definition experience wetting once whencleaning actually begins. Similarly, this differs from the trivialexample in which a passageway is actively dried out at the end of aconventional all-liquid cleaning cycle. In embodiments of the presentinvention, there may be repeated drying-outs and re-wettings of thesurface being cleaned.

Valving and Directions of Flow Through Particular Endoscope Channels

A typical endoscope has three possible regions of entry or exit of fluidfor use during a cleaning process: the control handle 90, the umbilicalend 70 and the distal end 100. Typically the distal end 100 may havegeometric constraints which would make it most likely that the distalend 100 would be used as an exit for flow used during cleaning. However,the connection points at the other two locations, i.e., the controlhandle 90 and the umbilical end 70, offer possibilities as to whichconnection points are inlets for flow and which connection points areexits for flow, and how valves are used to direct flow.

In general, for endoscope channels that have access points at or nearthe control handle 90, one possibility is that flow is introduced at thecontrol handle 90. This is illustrated in FIG. 16 a. Flow could beintroduced into the air/water cylinder well 126 in control handle 90.Entry of this flow can be controlled by valve V2. Flow could beintroduced into suction cylinder well 103 in control handle 90, and thisflow could be controlled by valve V3. Flow can be discharged to bothdistal end 100 and umbilical end 70.

Continuing with the configuration illustrated in FIG. 16 a, there mayfurther be connection points at the umbilical end 70 for the air (124)and water (123) channels. Flow through this connection point (121) maybe controlled by valve V4. There may also be connection point at theumbilical end 70 for the suction channel. Flow through this connectionpoint (101) may be controlled by valve V5. As illustrated in FIG. 16 a,both of these flows at the umbilical end 70 would be exiting flows.Either valve V4, V5 may be in either the open or the closed position. Ifvalve V4 is open while inlet valve V2 is open, there would be flowthrough the air (124) and water (123) channels in umbilical cable 80. Ifvalve V4 is closed, there would be no flow there even if correspondinginlet valve V2 is open. Similarly, If valve V5 is open while inlet valveV3 is open, there would be flow through the suction channel 102 inumbilical cable 80. If valve V5 is closed, there would be no flow thereeven if corresponding inlet valve V3 is open.

As illustrated, there are some channels which originate at or near thecontrol handle 90 and extend to the distal end 100, and are not presentin the umbilical cable 80. For such channels, flow may be supplied by aconnection at or near the control handle 90 and may proceed to thedistal end 100, similar to what was illustrated in FIG. 16 a. Forendoscopes that have a biopsy port 108, flow could be introduced to thesuction/biopsy channel 109 at biopsy port 108 which may be near or inthe control handle 90, and this flow could be controlled by valve V1.For endoscopes that have an elevator/wire channel 111, flow may beintroduced at the elevator/wire port 110, and this flow may becontrolled by valve V7. For endoscopes that have a forward water jetchannel 142, flow could be introduced at the forward water jet port 141which may be in the control handle 90 as illustrated (or for othermodels of endoscopes may be at the umbilical end). This flow may becontrolled by valve V6.

A source of liquid and gas flow may be applied to those valves which areinlet valves, namely V1, V2, V3, V6 and V7, or to any subset thereof. Asillustrated, the distal end 100 is unvalved. Flow can exit at the distalend 100 through any channel to which flow is supplied anywhere upstream.

Referring now to FIG. 16 b, there is illustrated an arrangement in whichflow through those channels which exist in the umbilical cable 80 is ina direction opposite of that illustrated in FIG. 16 a. Flow could beintroduced into the air/water connection 121 in umbilical end 70. Entryof this flow can be controlled by valve Va. Similarly, flow could beintroduced into suction connection 101 in umbilical end 70. Entry ofthis flow could be controlled by valve Vb.

If exit Valve Vd is open, flow in the air (124) and water (123) channelsmay exit at the control handle 90. If exit valve Vd is closed, flow inthe air/water channel may continue all the way to distal end 100.Similarly, if exit Valve Ve is open, flow in the suction channel 102 mayexit at the control handle 90. If exit valve Ve is closed, flow in thesuction channel 107 may continue all the way to distal end 100.

As illustrated, there are some channels which originate at or near thecontrol handle 90 and extend to the distal end 100, and are not presentin the umbilical cable 80. For such channels, flow may be supplied by aconnection at or near the control handle 90 and may proceed to thedistal end 100, similar to what was illustrated in FIG. 16 a. Forendoscopes that have a biopsy port 108, flow could be introduced to thesuction/biopsy channel 109 at biopsy port 108 which may be near or inthe control handle 90, and this flow could be controlled by valve Vc.For endoscopes that have an elevator/wire channel 111, flow may beintroduced at the elevator/wire port 110, and this flow may becontrolled by valve Vg. For endoscopes that have a forward water jetchannel 142, flow could be introduced at the forward water jet port 141which may be in the control handle 90 as illustrated (or for othermodels of endoscopes may be at the umbilical end). This flow may becontrolled by valve Vf.

A source of liquid and gas flow may be applied to those valves which areinlet valves, namely Va, Vb, Vc, Vf and Vg, or to any subset thereof. Asillustrated, the distal end 100 is unvalved. Flow can exit at the distalend 100 through any channel to which flow is supplied anywhere upstream.

It is still further possible that in some channels in the umbilicalcable 80, flow could be in one direction while in other channels flowcould be in the opposite direction.

Feedback Control of Liquid Flowrate

It is possible that, for some purpose such as achieving conditionsfavorable to cleaning, there is a desired relationship between liquidflowrate and gas flowrate. It is further possible that if gas issupplied from a source such as a constant pressure source, the gasflowrate through a passageway may change as a function of time. Forexample, as cleaning is accomplished, contaminants may be removed fromthe passageway, and the removal of contaminants may result in apassageway having less flow resistance. This, in turn, may result in anincrease in the flowrate of gas delivered by the gas source. If thishappens, or if in general the gas flowrate changes for any reason,having a pre-set or constant liquid flowrate may fail to achieve optimumor desired liquid flowrate for the gas flowrate which is actuallyoccurring at a particular time. A pre-set constant liquid flowrate for agas flowrate at one portion of the cleaning cycle may not always be themost appropriate liquid flowrate, such as if the flow resistancechanges.

Accordingly, the apparatus may include a feedback control loop. Suchapparatus is illustrated in FIG. 17. In such apparatus, gas may besupplied by a gas source 1710. Gas supplied by gas source 1710 may passthrough flowmeter 1720 which, at any given time, measures actual gasflowrate provided to the passageway being cleaned. Flow of liquid flowmay be provided by a liquid supply system which may be controlledresponsive to the gas flowrate measured by flowmeter 1720, so as toprovide a desired liquid flowrate. In this way, if the gas flowratechanges, the liquid flowrate can also change to maintain a desiredrelation to the gas flowrate. In FIG. 17, the liquid supply system isillustrated as comprising a concentrated cleaning solution metering pump1732, that provides liquid at a desired flowrate from a source ofconcentrated cleaning solution, and also a water metering pump 1734 thatprovides water. The water and the concentrated cleaning solution maythen meet and mix at junction 1750 so as to form a desired cleaningsolution. The desired cleaning solution may then come together with thegas flow at junction 1760 and be provided to the passageway 1780 to becleaned. The apparatus as illustrated allows the use of a relativelysmall or long-lasting container of concentrated cleaning solution, incombination with water which is generally available in substantialquantities, so that the container of concentrated cleaning solution needonly be replaced or refilled infrequently.

As is also discussed elsewhere herein, there may be apparatus whichprovides liquid and gas flow to two different passagewayssimultaneously. FIGS. 18 a and 18 b illustrate use of a feedback loop,so as to perform cleaning of two different passageways simultaneously.In both FIGS. 18 a and 18 b, there is provided a gas source 1810. FIGS.18 a, 18 b simply illustrate a generic liquid supply system 1840. Liquidsupply system 1840 could be a simple reservoir of cleaning solution inthe desired condition, or it could be a system which combinesconcentrated cleaning solution with water as described in connectionwith FIG. 17. There are provided two gas flowmeters 1820 a and 1820 b tomeasure gas flowrates delivered to respective flowpaths 1880 a 1880 b.The measured gas flowrates are reported to a control board 1835.

In FIG. 18 a, control board 1835 operates a first metering pump 1830 athat delivers liquid to flowpath 1880 a, and also operates a secondmetering pump 1830 b that delivers liquid to flowpath 1880 b. In FIG. 18b, control board 1835 operates a single metering pump 1830 whose outputis the summation of the desired liquid flowrate for flowpaths 1880 a and1880 b. This summation flowrate is then provided to proportional valve1845 which divides the summation flowrate appropriately betweenflowpaths 1880 a and 1880 b.

Of course, it would also be possible to provide a feedback system inwhich the gas flowrate is feedback-controlled responsive to a liquidflowrate.

Geometry to Promote Faithful Splitting or Distribution of Liquid+GasFlow

It can be seen from FIG. 19 a that a connector may connect to a cylinderwell 2060 in the control handle of the endoscope such that a particulartype of channel exits in two places from the cylinder well. One exit maylead toward the distal end of the endoscope and the other exit may leadtoward the umbilical end of the endoscope. It may be desirable that theconnector/introduce provide liquid+gas flow in two different directionssuch that the flow in each direction has approximately the sameliquid/gas ratio as the incoming flow; also don't want too muchseparation of the liquid from the gas. It can be appreciated that, ifgas and liquid are flowing simultaneously in a connector, and if theconnector involves a change of direction, gas is likely to achieve achange of direction more easily than the liquid, and the liquid has alikelihood of being carried by its own momentum so that it impacts adownstream feature of its flowpath near the change of direction. Inparticular, this may be a consideration if more than one exit existswith local geometries that are different from each other. The connectormay be designed with features such as smooth geometric transitions whichminimize the likelihood of maldistribution of liquid and gas flow.

It is possible that the forward direction of a particular endoscopechannel and the rearward direction of the same endoscope channel couldhave substantially similar local geometries where the connector wouldintroduce flow to the channel. Alternatively, it is possible that theforward and rearward directions of a particular endoscope channel couldhave different local geometries. Regardless of what the local geometriesare, it still is possible to use certain design strategies to providefor a faithful division of gas flow and liquid flow among the twodirections if both directions are open to flow simultaneously. Thesestrategies can also provide for good entry of gas+liquid flow even ifthere is a dedicated flowpath for a particular channel in the endoscope.

For example, sharp changes of direction can be avoided, especially inthe immediate vicinity of the entrance to the channel. Approaching theentrance to the channel, the flow of gas and the flow of liquid may bemade substantially parallel to each other for some distance. Flow ofliquid and flow of gas can be brought in using co-extruded lumens, onelumen to carry the liquid flow and another lumen to carry the air flow.It is possible that the co-extruded lumens could be coaxial, such aswith the liquid-carrying lumen being central and the gas-carrying lumensurrounding the liquid-carrying lumen. It is possible that the liquidcan be brought together with the gas only very close to the place wherethe combined fluids enter channel being cleaned. It is possible that thedesign can be such that any needed expansion of the gas flow has alreadytaken place somewhat upstream of the point where the gas and the liquidmeet each other.

Fixed-Position Connectors for Collective Channel Connections

In embodiments of the invention, there may be provided connectors thatinterface with an appropriate cylinder wall and direct flow as desired.Referring now to FIG. 19, there are illustrated fixed-positionconnectors that are capable of directing flow collectively to bothdirections of a channel.

FIG. 19 a illustrates an endoscope generically including some details ofcylinder wells within the control handle 90.

FIG. 19 b illustrates a possible design such that the liquid and gasflow which is supplied by the connector 2000A to a first channel in bothdirections is brought into the connector by a port 2030.

FIG. 19 c illustrates a possible design such that the liquid and gasflow which is supplied by the connector 2500A to a first channel in bothdirections is brought into the connector by a dedicated first port, andthe liquid and gas flow which is supplied by the connector to a secondchannel direction is brought into the connector by a dedicated secondport. An internal region associated with the first port is separated bya seal 2035 from an internal region associated with the second port.Seal 2035 may be an O-ring. As illustrated, the first port 2050 a islocated separate from the second port 2050 b. Alternatively, it would bepossible for one of the ports to be concentric with the other port.

Fixed-Position Connectors for Individual Channel Connections

Referring now to FIG. 20 a, there is illustrated a fixed-position (notactuator-driven) connector that is capable of directing flowindividually to either of two directions of a channel. This refers tototal of two distinct passageways that all connect to a cylinder well inthe control handle. For example, the cylinder well 2010 may connect to asuction channel having a first exiting direction to a distal end of theendoscope and a second exiting direction to an umbilical end of theendoscope. As illustrated, there are two inlet ports 2020 a, 2020 b, andcorresponding introduction paths 2021 a, 2021 b. Each port andintroduction path is associated with a particular direction of aparticular channel within the endoscope. As illustrated, introductionpath 2021 a and introduction path 2021 b are coaxial with each other,although they do not have to be. Within connector 2000, there may beseal 2030, such as an O-ring, that may define separation betweenrespective introduction paths or between an introduction path and theexterior. Seals may bear against corresponding interior surfaces ofcylinder well 2010 when the connector 2000 is in place in the cylinderwell 2010. As illustrated, the passageway that connects with thecylinder well 2020 a most deeply into the cylinder well 2010 is thesuction channel in the direction to the umbilical end of the endoscope.Flow to the suction channel in the direction to the umbilical end isdelivered via the first introduction path 2021 a by the port 2020 awhich is on the centerline of the connector 2000. A second passageway,which is the suction channel in the direction to the distal end of theendoscope, is the next deepest connection point in the cylinder well2010. Flow is delivered to the suction channel in the direction to thedistal end by a second introduction path 2021 b that is concentric withthe first introduction path 2021 a but does not extend as far into thecylinder well 2010 as does the first introduction path 2021 a. Usingthis design of connector, it is possible to supply flow to any of thepassageways independently of any other passageways, in any timewisecombination such as simultaneously or sequentially or any combinationthereof.

Referring now to FIG. 20 b, there is illustrated a non-actuator-drivenconnector 2500 that is capable of directing flow individually to eitherof two directions of two different channels. This refers to a total offour distinct passageways that all connect to a cylinder well in thecontrol handle. For example, the cylinder well 2060 may connect to anair channel in the direction of the distal end; an air channel in thedirection of the umbilical end; a water channel in the direction of thedistal end; and a water channel in the direction of the umbilical end.As illustrated, there are four inlet ports 2070 a, 2070 b, 2070 c, 2070d, and corresponding introduction paths 2071 a, 2071 b, 2071 c, 2071 d.Each port and introduction path is associated with a particulardirection of a particular channel within the endoscope. At least some ofthese introduction paths may be coaxial with another introduction path.Within connector 2500, there may be seals 2080 a, 2080 b, 2080 c, suchas O-rings, that may define separation between respective introductionpaths or between an introduction path and the exterior. Seals may bearagainst corresponding interior surfaces of cylinder well 2060 when theconnector 2500 is in place in the cylinder well 2060. As illustrated,the passageway that connects with the cylinder well 2060 most deeplyinto the cylinder well 2060 is the water channel 2178 in the directionto the umbilical end of the endoscope. Flow to the water channel in thedirection to the umbilical end is delivered via the first introductionpath 2071 a by the port 2070 a which is on the centerline of theconnector 2500. A second passageway, which is the water channel 2176 inthe direction to the distal end of the endoscope, is the next deepestconnection point in the cylinder well 2060. Flow is delivered to thewater channel in the direction to the distal end by the port 2070 b viaa second introduction path 2071 b that is concentric with the firstintroduction path 2070 a but does not extend as far into the cylinderwell 2060 as does the first introduction path 2071 a. Still less deepinto the cylinder well 2060 is a connection point for the air channel2174 in the direction of the umbilical end. This is supplied by thirdintroduction path 2071 c which is supplied by third port 2070 c. Thirdintroduction path 2071 c may or may not be concentric with otherintroduction paths. The connection point least recessed in the cylinderwell is the air channel 2172 in the direction of the distal end of theendoscope. Fourth port 2070 d and fourth introduction path 2071 d bringflow to this passageway. Each introduction path may be controlled by itsown dedicated valve (not illustrated). Using this design of connector,it is possible to supply flow to any of the passageways independently ofany other passageways, in any timewise combination such assimultaneously or sequentially or any combination thereof.

Of course, other geometries and designs of connectors are also possible.In general, it is possible to use any connection geometry that connectsfour ports to four passageways in a defined manner and whichaccommodates the geometry of the cylinder well and the passageways thatconnect to the cylinder well.

Connector Having an Actuator

It is further possible that the connector could comprise an actuator2130 which definitively opens or closes or establishes a path for flowto a certain channel or channels of the endoscope or similar medicaldevice. This is illustrated in FIG. 21 for an actuated connector thathas four possible positions. FIGS. 21 a, 21 b, 21 c and 21 drespectively illustrate all four possible positions of the actuator.

As illustrated, the connector 2100 may comprise two seals 2112 and 2114,with flow being delivered between the two seals 2112 and 2114. In FIG.21 a, the position of the actuator 2130 is such that flow is deliveredto the passageway connection 2172 which is closest to the exterior ofthe cylinder well 2060. As illustrated, this passageway connection isthe air channel in the direction of the distal end. FIG. 21 billustrates the actuator in a position such that flow is delivered tothe next most outermost position which as illustrated is the passagewayconnection 2174 to the air channel in the direction of the umbilicalend. FIG. 21 c illustrates the actuator in a position such that flow isdelivered to a still more inner-located position which as illustrated isthe passageway connection 2176 water channel in the direction of thedistal end. FIG. 21 d illustrates the actuator in a position such thatflow is delivered to an innermost position which as illustrated is thepassageway connection to water channel 2178 in the direction of theumbilical end.

The position of the actuator 2130 may be controlled by a microprocessoror similar control system which may also operate other aspects of anautomated endoscope reprocessor or may have knowledge of the status ofother components of the reprocessor.

Similarly, it would be possible to design an actuated connector thatonly has two positions of the actuator. It would also be possible todesign an actuator-driven connector able to selectively connect to adesired channel, which involves rotation of a rotatable member, perhapswith a seal. It would still further be possible to design anactuator-driven connector which uses both rotary and translationalmotion.

With an actuator-driven connector, it may not be possible tosimultaneously provide flow to all of the passageways that connect to aparticular cylinder well. It may be necessary to provide flow to onepassageway or group of passageways to the exclusion of others, and thenlater to provide flow to another passageway or group of passageways tothe exclusion of others.

Latches

It is further possible that the connector could comprise latches whichgrab onto a feature of the endoscope itself to maintain secure andcorrect positioning of connector with respect to endoscope. For example,features of the connector could interact with features of the endoscopeso that there is only one permitted orientation of the connector withrespect to the endoscope. Alternatively, it may be desired that theconnector could be permitted to be oriented with respect to theendoscope in more than one permitted orientation, or in any number ofpermitted orientations. If desired, the connector could be appropriatelydesigned to permit this situation.

Introducer (Providing Extra Flowpath Length Before Cleaning)

It is believed, although again it is not wished to be limited to thisexplanation, that when gas flow and liquid flow are first introducedinto a passageway from a connector or significant change of flowgeometry or direction, there is eventually established a flow regimethat is somewhat repeated thereafter further downstream and may bedescribed as a fully established flow regime. However, before thathappens, there may be an initial region, close to the inlet or change offlow geometry or direction, in which some other flow regime exists. Itis possible that even if fully-established conditions further downstreamare good for cleaning, conditions in the initial region might not be sodesirable for cleaning. It is possible that establishment of appropriateconditions for cleaning, such as fully-established flow, requires acertain length of flowpath to develop or establish themselves.Accordingly, it is possible that a connector to the endoscope or otherdevice to be cleaned may comprise a port or ports for introduction oftwo phases either separately or at a single port, and may furthercomprise an appropriate length of passageway which has a cross-sectionalshape identical to or similar to that of the passageway to be cleaned,and has a cross-sectional area which is within a factor of two (ineither direction) of the cross-sectional area of the passageway to becleaned. It is further possible that such introduction region can beprovided for use in a condition which is at least substantially cleanprior to performing the cleaning procedure. The introducer may be cleanfrom being used during a previous cleaning procedure. In such event,even if flow conditions inside the introduction region are themselvesnot optimum for cleaning, at least the introduction region will notcontain contaminants that could be washed downstream into or through thepassageways which are intended to be cleaned.

Uniqueness of Supplied Flow

In embodiments of the invention, for any of these described connectors,whether static or actuated, it is possible to supply a predeterminedflow (the liquid flowrate and the gas flowrate can both bepredetermined) to a particular passageway such as a particular channelin an endoscope or a particular direction of a channel in an endoscope.In particular, if an open connection exists to only one passageway atany given time, then it is assured that the liquid/gas ratio in thatpassageway is definitely known. Also, the sequencing of supplying flowto particular passageways can be definitively determined.

For example, for a given channel such as the air channel, the flow couldbe directed for one period of time from the control handle toward thedistal end of the endoscope and at another period of time could bedirected from the control handle to the umbilical end of the endoscope.If a connector serves two fluid channels of the endoscope, which may bedesignated first channel and second channel, it is possible that for oneperiod of time the connector could direct flow to one direction of thefirst channel and for another period of time the connector could directflow in the opposite direction of the first channel, and for yet anotherperiod of time the connector could direct flow in one direction of thesecond channel and for yet another period of time the connector coulddirect flow in the opposite direction in the second channel. Of course,the sequence could be arranged in any arbitrary manner, and depending onthe design of the connector, it may be possible to perform some of theseactions simultaneously with other of these actions.

Of course, for any directing of flow to a particular channel in aparticular direction, the liquid flowrate or the gas flowrate or bothcould be chosen uniquely for that situation. As discussed elsewhereherein, choice of an optimum liquid flowrate can be influenced by thediameter of a particular channel, the length of the channel, andpossibly other parameters as well. For example, the liquid flowrate forthe forward direction of a particular channel need not be identical tothe liquid flowrate for the backward direction of that same channel fromthe cylinder well at the control handle.

The apparatus as described herein allows separate conditions of liquidand gas flow for each channel of the device so as to produces optimalflow of rivulets and rivulet fragments for contaminant removal in eachchannel. Liquid flowrate and any other conditions can be unique forparticular inside diameter of passageway, for particular length ofpassageway, for a maximum allowable pressure for a particularpassageway, and for any other feature unique to a particular passageway.Although it would be convenient in a practical sense that the sameliquid (including composition and concentration of surfactant) be usedfor all channels within a given endoscope, it is further possible that adifferent liquid could be used for different channels.

It is possible that an apparatus can have connectors that are unique toa particular brand or model of endoscope, so the apparatus can know acertain amount of information about what is being cleaned simply byvirtue of the connectors. Furthermore, it is possible that the apparatuscan read information about what is being cleaned by reading a bar codeor similar identifying information. It is even possible that theapparatus can store information about a particular endoscope. Any suchinformation can be used for selecting operating conditions for aparticular endoscope or for particular passageways of a particularendoscope.

Complex medical devices such as endoscopes may contain variouspassageways differing in diameter, construction and length. It can beappreciated from the discussion elsewhere herein that desirable flowinput conditions may be different for different channels of anendoscope. The apparatus may be able to provide separate conditions ofliquid and gas flow for each passageway of the device so as to producesoptimal flow of liquid entities such as rivulets and rivulet fragmentsfor contaminant removal in each passageway or channel.

In general, any particular channel of an endoscope could experience atreatment sequence which differs from that of other endoscope channelsin any aspect of the chronology of events.

Cleaning a Passageway that has a Wire Inside it

It is also possible to use the described apparatus and methods to cleana passageway that is generally cylindrical with a wire located in theinteriors. Such a passageway may be an elevator channel (which may alsobe referred to as an elevator wire channel) in an endoscope. Theelevator wire may be used to steer the tip of the endoscope.

The elevator channel and the wire, taken together, may define an annularspace, if the wire is located at least somewhat concentrically with thepassageway. The dimensional space between the elevator wire and thechannel which surrounds the elevator wire may be approximately 0.18 mm.Of course, it is also possible that the wire could be eccentric withrespect to the channel, or could even contact the channel interior.Different ones of such configurations could exit at different placesalong the length of the elevator channel and the wire therein. It isbelieved, although it is not wished to be restricted to thisexplanation, that rivulet droplet flow can contact or slide along boththe internal surface of the channel and the external surface of thewire, and can clean both such surfaces.

Typically the elevator channel is pressure-tested to a higher pressurethan any other channel of the endoscope, so it may be possible to use ahigher gas pressure in the elevator channel, for example, 60 or 80 psig.

Eductors and External Cleaning

In embodiments of the invention, apparatus for the external cleaning ofan endoscope may comprise an eductor 800, which is a flow amplificationdevice. This is illustrated in FIG. 22 a. An eductor 800 may comprise anentry converging region 822, followed by a body region 824 that may beof at least approximately constant internal cross-section, followed by adiverging or diffuser region 826. All of these regions 822, 824, 826 maybe aligned in a common longitudinal direction. These regions 822, 824,826 may be cylindrical. The eductor 800 may further comprise a nozzle830 that discharges inside the eductor 800 in approximately thelongitudinal direction. As a pressurized cleaning solution is pumpedthrough the nozzle 830 at a high velocity, the surrounding liquid isentrained/pulled into the main stream. The combination of pumped andpulled flows can be significantly larger than the flow rate of theejected stream through the nozzle 830 itself. For example, an eductor800 can pull up to 3 to 5 additional flow volumes from the surroundingliquid for each volume pumped through the nozzle 830. The liquid can bepumped by a recirculating pump 840 which draws liquid from basin 850within which the endosocope(s) are enclosed. Due to this multiplyingeffect, a relatively small pump 840 can be used to circulate relativelylarge flowrates of cleaning solution for cleaning the external surfacecleaning of endoscopes. As illustrated, pump 840 draws fluid from basin850 and returns it through the nozzles 830 of all of the eductors 800.

As illustrated in FIG. 22 a, there are eight eductors 800, two in eachcorner of basin 850. It can be realized that a single eductor 800 canonly create a strong flow to cover a single angle of view of a portionof the endoscope which may be coiled in the basin 850. Therefore, it ispossible to use a plurality of eductors 800 each facing a particularportion of the endoscope so as to in combination form an effective flowpattern for exterior surface cleaning. As illustrated in FIG. 22 a, thebasin 850 may be rectangular or approximately square having fourcorners, and at each corner there may be two eductors 800 pointing fromthe corner towards the interior of the basin 850, with each of the twoeductors 800 pointing in slightly different directions. Of course, othershapes of basin 850 are possible also.

We have found that it is important to integrate both impingement andagitation effects created by the eductor system to achieve the bestcleaning results for cleaning external surfaces of endoscopes.Accordingly, the basin may generally be designed with special features,including: proper cavities to accommodate two endoscopes. There can be acombination of eductors located in corners and eductor located on walls.Eductor design and basin design are further described in Examples.

An endoscope reprocessing apparatus may further comprise a spray arm orspray nozzles located above the elevation of the endoscope(s) whenendoscope(s) are being cleaned. Such spray may, for example, be used forrinsing the external surfaces of the endoscope(s) after cleaning of theexternal surfaces of the endoscope(s) has been performed. Of course, itis also possible for such spray nozzles to be used during cleaning ofexternal surfaces of the endoscope(s). These are illustrated in FIG. 22d and FIG. 22 e.

It is further possible that eductors can be caused to flow in a sequenceor pattern, rather than all of the eductors flowing all of the time. Forexample, some can be on and some can be off at different times, so as tofurther create agitation. For example, the patterning and timing ofeductor operation could be such as to create swirl in one or anotherdirection or various directions sequentially. There may also be anoverhead spray which may be useful for rinsing, for example.

EXAMPLES

The following examples are shown as illustrations of the invention andare not intended in any way to limit its scope.

Examples 1-7 illustrate the method of determining hydrodynamic modes offlow, mapping these modes as a function of flow rates for tubes ofdifferent diameters and identifying conditions that produce RivuletDroplet Flow. The tubes employed are of diameters that cover thechannels encountered with typical endoscopes.

Example 1 Method to Construct Flow Regime Maps

This method was developed to identify and define the flow regime(surface flow entities and their distribution) on the channel wall atseveral positions along channel length from inlet to outlet as afunction of the operating parameters. Operating parameters include:channel diameter and length, liquid flow rate, air pressure, air flowrate and velocity, and surfactant type and concentration. The methodenables identification and optimization of Rivulet-Droplet-Flow forvarious endoscope channels ports. In addition, the flow regimes atdifferent positions along channel length has been used to define theoperating conditions of the cleaning cycles necessary to achievehigh-level cleaning of the entire channel surface area. As will becomeapparent, the flow regime (collection of fluid flow elements) varies asfunction of distance from channel inlet to exit and this necessitatesdifferent treatment conditions to achieve optimal results for each typeof channel. Although the method is illustrated with RDF flow, the methodcan clearly be used to map DPF and DPDF flow regimes by introducing theliquid plug instead of a rivulet.

Apparatus: Apparatus: The apparatus 200 illustrated schematically inFIG. 23 allows optical examination of transparent endoscope channels, tocontrol the flow conditions used in the test and to measure alloperating parameters both under static and dynamic conditions. Theapparatus 200 consists of a source of compressed air 202 (Craftsman 6HP, 150 psi, 8.6 SCFM @40psi, 6.4 SCFM @90psi, 120V/15amp), variousconnectors and valves 204, 206, pressure regulators 208, 210 a flowmeter 212, pressure gauges 214, 216, 218, a metering pump 220 (FluidMetering Inc.,Model QV-0, 0-144 ml/min), metering pump controller 222(Fluid Metering Inc., Stroke Rate Controller, Model V200), variousstands and clamps (not shown), various tube adapters (not shown), animaging system 224 which includes a microscope, digital camera, flash,and various illumination sources (not individually shown in FIG. 12 butidentified below).

The compressed air source is a 6-HP (30-gallon tank) Craftsman aircompressor 202. The compressor 202 has two pressure gauges, one for tankpressure 214 and one for regulated line pressure 216. The maximum tankpressure is 150 psi. The compressor 202 actuates when the tank pressurereaches 110 psi. The line pressure is regulated to 60 psi for themajority of the tests, with the only exceptions being the high pressuretest (80 psi) used to define the hydrodynamic mode for the 0.6-mm (ID)“elevator-wire channel”. The regulated compressed air is supplied to asecond regulator via 15′ of ⅜″ reinforced PVC tubing. The secondregulator is used to regulate the pressure for each test. The air thenfeeds into a 0-10 SCFM Hedland flowmeter 212 with an attached pressuregauge 218. This gauge 218 is used to set the test pressure via thesecond regulator 210 that precedes it, as well as to read the dynamicpressure during the experiment. The flow meter 212 feeds into a “mixing”tee 226, where liquid is metered into the air stream via a FMI “Q”metering pump 220. The metering pump 220 is controlled by a FMI pumpcontroller 222. The outlet of the mixing tee 226 is where adapters 228for varying model endoscope tube diameters 230 are connected.

To acquire an image of the flow mode inside the channel, we used aBausch and Lomb Stereozoom-7 microscope (1×-7×), a camera to microscopeT-mount adapter, a Canon 40D digital SLR camera, and a Canon 580EXspeedlite. The camera to microscope adapter's T-mount end is bayonetedto the camera and the opposite end is inserted in place of one of theeyepieces on the binocular microscope. The flash is attached to thecamera via a hot shoe off camera flash cable and directed into amirror/light diffuser mounted below the microscope stage. Themirror/diffuser is a two sided disc with a mirror on one side and a softwhite diffuser on the opposing side. This can be rotated to change theangle of the light that is directed towards the stage as well as toswitch between the two sides. The microscope also has an open portholeon the rear-bottom that allows for light to be directed onto themirror/diffuser. A Bausch and Lomb light (Catalog #31-35-30) is insertedinto this porthole and used in conjunction with the Canon 40D's liveview feature for live viewing as well as for focusing. The live viewfeature shows a real time image on the 3″ LCD screen on the back of thecamera. The channel to be photographed is placed on the microscope stageand taped into place. Photographs were taken with an exposure time of1/250th of second with the flash on full power using an optional remoteto reduce vibration. Certain tests required single shots while othertests required photographs to be taken in “burst mode.” In burst modethe camera shoots 5 frames per second at equal intervals. The images arestored on a 2 GB compact flash card and transferred to a PC via amulti-slot card reader. Images are processed (for clarity) in Adobe CS3and analyzed one by one with the naked eye either on a 22″ LCD monitoror via color prints from a color laser printer. The latter was used toanalyze and compute treatment number under different conditions.

Model Test: Teflon tubing (McMaster-Carr Company) with differentinternal diameters and lengths was used to create the flow regime maps.The gas pressure for these experiments was set at desired value from 0to 80 psi at the second regulator. The liquid flow rate was varied froma low flow rate of about 3 mL·min to a high flow of about 120 mL/min, orhigher if necessary. Images were taken at generally 5 positions measuredfrom the inlet along the length of the each tube (generally around twometers in length): 1) 35-45 cm; 2) 65-75 cm; 3) 110-120 cm; 4) 143-165cm; and 5) 190-210 cm near end of the tube. At each position,microphotographs were taken at a range of flow rates, from the low flowrates to the high flow rates with a total of 5 and 9 flow rate steps ineach test. 20-30 photographs were taken for each position for analysis.

Image Analysis and Map Construction: The image analysis consisted ofexamination of all microphotographs from each combination of flow ratesand channel positions to determine the prevailing surface flow entitiesand hydrodynamic mode. The surface flow entities of interest includedrivulets (straight and meandering), droplets (random), linear dropletarrays (LDA), sub-rivulets, sub-rivulets “fingering” off of the mainrivulet, sub-rivulet fragments, turbulent/foamy rivulets, liquid films,foam, and all transition points between these features. These liquidfeatures were used to describe various modes of flow (flow regimes) andthese modes were then put into a “map” which shows the prevailing modesof flow as a function of distance from tube inlet at different liquidflow rates, at the selected air pressure. Qualitative features were usedto define the flow regimes observed and quantitative analyses of imageswere used to compute the Treatment Number.

Descriptions of liquid features and hydrodynamic modes used in mappingflow regimes: The following descriptive definitions are used to classifyindividual surface flow entities which are observed when a liquid isintroduced into channel as a rivulet stream and gas is simultaneouslyallowed to flow under pressure in the tube. These terms provide aconsistent definition of flow elements for the classification of flowregimes defined below.

1. Rivulet: A continuous stream of liquid normally covering the entirelength of tube and usually more prevalent near the inlet sections of thetube. Rivulets, depending on their velocity, liquid composition, andtube surface micro-roughness can either be perfectly straight or“kinked.” In both cases the rivulet could be “stuck” (no meandering) orcould meander (“meandering rivulets”) about the tube surface reachingsides or ceiling of the tube due to transversal movement.

2. Droplets: Single beads of liquid that can either be static or movingalong the surface of tubing and are not connected to any other feature.These droplets can range from 5 microns to 50 microns. Droplets can bedistributed at random, or exist as linear array split from trailing endof rivulet fragments.

3. Sub-rivulets: Cylindrical bodies in the form of long continuousliquid threads that break off of or finger from the main rivulet. Theyare generally much thinner in comparison to the main rivulet. Dimensionsof subrivulets depend on the flow conditions and liquid composition andcan range from 100 microns to 300 microns.

4. Sub-rivulet fragments: When sub-rivulets break apart they producerivulet fragments. A sub-rivulet normally becomes unstable and splitsinto several equal rivulet fragments that form a linear rivulet fragmentarray (LRFA). Each fragment becomes tear shaped or pill shaped with anadvancing and receding contact angle. The advancing contact angle isnormally high (e.g., greater than 60 degrees) while the receding contactangle at the trailing edge of the liquid feature is much lower (e.g.,less than 50 degrees). Droplets normally split from the trailing end ofa rivulet fragment. These droplets frequently form linear droplet arrays(LDA).

5. Liner droplet arrays (LDA): Long arrays of small (20 microns to 200microns) droplets deposited on the tube surface, normally formed fromthe trailing end of a sub-rivulet fragment.

6. Turbulent/foamy rivulet: The main rivulet often reforms near the endof tube in a more chaotic and less structured fashion, and oftenincludes discrete dispersed air bubbles and foam (multiple dispersed airbubbles in close proximity). This rivulet does not tend to meander asmuch as the main rivulet in the early sections of the tube near theinlet. This foamy mode normally leads to formation of a thick liquidfilm that covers the entire cross-section of tube depending of thesurfactant or surfactant mixture used.

7. Film: A complete annular liquid film covering the entire tube or tubesection, normally without traces of air bubbles or foam.

8. Foam: A prevalence of air bubbles dispersed in the liquid phasenormally present in the entire tube cross section.

The term “fragments” is used to encompass all surface flow entities thatare derived from the initial rivulet and include: droplets, sub-rivuletsand sub-rivulet fragments (collectively cylindrical bodies) and lineardroplet arrays (LDA).

Generalized Flow Regimes: The following qualitative descriptions areused to qualitatively classify the predominant flow regimes or “modes offlow” that are observed during the experiment. Their typical appearanceis given in the photographs and corresponding schematic drawings in FIG.5 b.

Sparse/Dry (FIG. 5 b-A): A mode of flow generally observed when theliquid flow rate is very low. The main rivulet is skinny and tends to bebroken (not continuous). There are some stray sub-rivulet fragments andrandom droplets, but these features are few and far between.

Single Rivulet (FIG. 5 b-B): When the liquid flow rate reaches acritical level the main rivulet forms and is continuous. The mainrivulet can be straight or kinked, can be stationary or meanderingdepending on the gas velocity. The rivulet thickens with flow rate anddoes not break apart. Other features are absent in this flow modebecause all of the liquid is contained in the rivulet.

Ejection Zone (FIG. 5 b-C): When a high enough gas velocity (furtherdistance from the tube inlet or higher pressure) and/or liquid flow rateis achieved, the sub-rivulets begin becomes instable and eject or splitfrom the main rivulet. This mode also contains a few sub-rivuletfragments and random droplets.

Rivulet-Droplet-Flow (FIG. 5 b-D): Main rivulet may or may not bepresent. Sub-rivulets, sub-rivulet fragments and droplets prevails.Sub-rivulet fragments leave linear droplet arrays. Random droplets arealso present.

Film/Foam (FIG. 5 b-E): Complete coverage of the tube with either a filmand/or foam.

Example 2 Flow Regime Map for 2.8 mmm Channel

In this example the methods and apparatus of Example 1 were used toconstruct the flow regime map for a tube with 2.8 mm ID and 2 meterlength. The following operating condition were employed: air pressure(30 psi), air flow rate (about 5.0 SCFM), air temperature (21C-ambient), liquid temperature (21 C-ambient). The cleaning liquidincluded SURFYNOL® 485 and AO-455 (Composition 10A in Table 5). Theliquid flow rates ranges from 0 ml/min to 29 ml/min with 7 flow ratesteps in between for a total of nine flow rates. In this example thepositions for photographs were 45 cm, 73 cm, 112 cm, 146 cm, and 196 cm.Microphotographs were collected at each position and each liquid flowrate, and then analyzed to construct the flow regime map given in FIG. 7c. The following flow modes were observed at each position along thetube (distance from inlet) as a function of liquid flow rate andposition along the tube.

At the 45-cm point, the flow mode is sparse/dry up to about 6.5 mL/minat which point it transitions to the single rivulet flow mode whichcontinues with increasing liquid flow rate up to 29 mL/min. At thisposition, the gas velocity is low near the entrance of the tube andinsufficient to produce rivulet instability or fragmentation. Therivulet that forms at this position which appears above 6.5 mL/minliquid flow rate exhibits some meandering due to hydrodynamicinstability.

At the 73-cm point, the flow mode is sparse/dry up to 5 mL/min flowrate. As the liquid flow rate increases, the flow mode transitions intothe single rivulet mode. The single rivulet flow mode continues up toabout 18 mL/min at which point it transitions into an ejection zone modewhere sub-rivulets split from the main liquid rivulets. The ejectionzone continues up until 29 mL/min. The ejection zone mode appears toarise due to further instability of the liquid on the tube wall whichleads to splitting of sub-rivulets from the main rivulet. The mainrivulet tends to meander due to transversal movements.

At the 112-cm point, the flow mode is sparse/dry up to about 4.0 mL/minflow rate at which point the flow mode transitions to the single rivuletflow. The single rivulet flow continues up to about 17 mL/min at whichpoint it transitions into an ejection zone. The ejection zone continuesup to 23 mL/min at which point it transitions to a film/foam mode. Thefilm/foam mode continues up to 29 mL/min.

At the 146-cm point, the flow mode is sparse/dry up to about 3 mL/min atwhich point the flow mode transitions to single rivulet flow. The singlerivulet flow mode continues up to 12 mL/min at which point ittransitions into rivulet-droplet flow (RDF) with various fragments andsurface flow entities observed. The RDF mode continues up to 22 mL/minat which point it transitions to the film/foam mode. The film/foam modecontinues up to 29 ml/min.

At the 196-cm point, the flow mode is sparse/dry up to 2 mL/min at whichpoint the flow mode transitions to the single rivulet flow mode. Thesingle rivulet flow mode continues up to 12.5 mL/min at which point ittransitions into the RDF mode. The RDF mode continues up to 21 mL/min atwhich point it transitions to the film/foam mode. The film/foam modecontinues up to 29 mL/min.

The above data is plotted as a flow regime map as a function of theposition along tube length from inlet (0 cm) to outlet (200 cm) and theliquid flow rate at a constant air pressure in FIG. 7 c. The mapprovides a convenient representation of defines the different flow modesobserved at each position along the tube length at the different liquidflow rates. The region within the map that provides optimal RDF flow canthus be identified and the controlling parameters selected (e.g., liquidflow rate at a particular gas pressure.

In the case of the 2.8 mm ID tube, liquid flow rates between about 16 toabout 22 mL/min appear to provide liquid flow features that would effecthigh level cleaning over most of tube length. For illustration, the 19mL/min liquid flow rate the sparse/dry mode is minimized (limited toonly short section near entrance) while both the ejection and RDF modecover most of the tube length without formation of film or foam near theexit of the tube. At very low liquid flow rates (0 to 10 mL/min), flowmodes are characterized by sparse/dry mode and single rivulet mode;under such conditions the entire surface of the tube cannot beadequately cleaning due to the small amount of surface flow entities andto the low Treatment Number in this case. Treatment time needs to beextended in this case and this becomes impractical in cleaningendoscopes and other medical devices. On the other hand, at very highliquid flow rates, most of the tube length will be dominated by film andfoam which result in covering the contaminants with a liquid film, acondition that does not produce high-level cleaning. It should thus beappreciated that cleaning according this method with a single liquidflow rate might not cover the entire length of the tube if cleaning timeis short, and that using more than one liquid flow rate or utilizingalternative flow regimes, e.g., DPF or DPDF regimes, to create surfaceflow entities with moving three phase contact lines may be required.This can be achieved by utilizing alternating liquid plug and gas flowfor a part or all of the cleaning cycle. Using other surfactant mixturesmay also produce other flow maps under the same conditions depending ofthe nature of surfactants. length of the tube if cleaning time is short,and that using more than one liquid flow rate or utilizing alternativeflow regimes, e.g., DPF or DPDF regimes, to create surface flow entitieswith moving three phase contact lines may be required. This can beachieved by utilizing alternating liquid plug and gas flow for a part orall of the cleaning cycle. Using other surfactant mixtures may alsoproduce other flow maps under the same conditions depending of thenature of surfactants.

The methods of Example 1 and analysis procedure Example 2 were employedin Examples 3-7 to construct flow regime maps for tubes of differentdiameters.

Example 3 Flow Regime Map for 1.8-mm Tube

The conditions used were: air pressure (30 psi); air flow rate (about3.0 SCFM); air temperature (ambient @21 C); liquid temperature (ambient@21 C). The test cleaning liquid included Surfynol 485 (0.036%) andAO-455 (0.024%). In this example the liquid flow rates range was from3.5 mL/min to 12.5 mL/min with 5 flow rate steps in between for a totalof seven flow rates. The positions examined with photographs were:36-cm, 73-cm, 112-cm, 146-cm, and 188-cm, all measured from tube inlet(0-cm). The map for the 1.8-mm tube found for the above conditions isshown in FIG. 7 b.

The flow maps for the 1.8-mm (FIG. 7 b) and the 2.8-mm channels (FIG. 7c) are clearly different. The RDF and ejection zones are shiftedobserved in the 1.8 mm tube are shifted to lower liquid flow ratesrelative to the 2.8 mm tube and cover a greater fraction of the tubelength.

The 1.8 mm tube is important since it represents the dimension of theair, water and auxiliary channels in many flexible endoscopes. The flowmode map (FIG. 7 b) indicates that liquid flow rates between 6.0 to 9.0mL/min appears to provide an acceptable range to achieve high-levelcleaning at 30 psi air pressure according to the methods of thisinvention). In this liquid range, rivulets, subrivulets andfragmentation can be created on most of the tube surface. High liquidflow rates with this surfactant mixture (Composition 10A in Table 5)lead to film/foam flow mode which prevents the formation of surface flowentities that produce high detachment force.

Example 4 Flow Regime Map for 4.5 mm Tube

The test conditions were: air pressure (30 psi); air flow rate (about6.0 SCFM); air temperature (ambient @21 C); liquid temperature (ambient@21 C). The cleaning liquid was the same as in Examples 2 and 3. Theliquid flow rates ranged from 13 mL/min to 69 mL/min with 7 flow ratesteps in between for a total of nine flow rates. The positions along thetube used for microphotographs were: 28-cm, 67-cm, 123-cm, 162-cm, and196-cm. The map for the 4.5 mm tube found for the above conditions isshown in FIG. 7 d and significantly differs from the narrower diametertubes described in Example 2-3.

At the 28-cm point the 4.5 mm tube is in the ejection mode from thestart and transitions into RDF at 33 mL/m. The RDF mode continues until62 mL/m at which point it transitions into the film/foam mode. At the67-cm point the 4.5 mm tube is in RDF until 60 mL/m at which point ittransitions into the film/foam mode. At the 123-cm point the 4.5 mm tubeis in RDF until 39 ml/m at which point it transitions into the film/foammode. At the 162-cm point the 4.5 mm tube is in the RDF mode until 35mL/min at which point it transitions into the film/foam flow. At the196-cm point the 4.5 mm tube is in RDF until 33 ml/m at which point ittransitions into the film/foam mode. Due to the larger diameter tube thegas velocities in the 4.5 mm tube are much higher and ejection occursearlier in the tube (closer to the entrance) and the RDF mode surfaceflow entities is sustained over a larger portion of the tube and over alarger range of flow rates. In the 4.5 mm tube still lower flow ratesare lead to the sparse/dry flow mode.

Example 5 Flow Regime Map for 6.0 mm Tube

The test conditions were: air pressure (30 psi); air flow rate (about8.0 SCFM); air temperature ambient @21° C.; cleaning solutiontemperature ambient temperature @21° C. The test cleaning liquid in thisexample was the same as in Example 1. The flow rates ranges from 25ml/min to 85 ml/min with 7 flow rate steps in between for a total ofnine flow rates. The positions for photographs were: 23-cm, 56-cm,118-cm, 163-cm, and 196-cm. The map for the 6 mm tube found for theabove conditions is shown in FIG. 7 e and is qualitatively similar tothe map for the 4.5 mm ID tube but differs significantly from those ofthe narrower diameter tubes described in Example 2-3).

At the 23-cm point, the single-rivulet flow mode is observed until about32 mL/min at which point it transitions to the ejection flow mode. Thismode continues up until about 62 mL/min at which point the flowtransitions into the RDF mode. At the 56-cm point, the single-rivuletflow is observed up until 32 mL/min at which point it transitions intothe RDF flow mode. The RDF mode is observed until about 80 ml/min atwhich point it shifts to the film/foam mode. At the 118-cm point, thesingle-rivulet flow is observed up until about 32 mL/min at which pointit transitions into the RDF flow. The RDF mode is observed until about65 ml/min at which point it shifts to the film/foam mode. At the 163-cm,single-rivulet flow mode is observed up until about 32 mL/min at whichpoint it transitions into mixed the RDF mode. The RDF mode is observeduntil 62 mL/min at which point it shifts to the film/foam mode. At the196-cm point, the RDF mode is observed until 65 mL/m at which point itshifts to the film/foam mode. This map closely resembles the 4.5-mm tubemap (FIG. 7 d). However, due to the high air flow rate obtained underthese above conditions, the RDF mode can be achieved at most of the tubelength, except at a short segment near the entrance of the tube.

Comparison of FIGS. 7 b and 7 c with FIGS. 7 d and 7 e indicates that itis easier to achieve optimal zones of RDF flow over most of tube lengthwith larger diameter 4.5 mm and 6 mm tubes.

Example 6 Flow Regime Map for the 0.6 mm Tube @30 psi Air Pressure

The test conditions were: air pressure (30 psi); air flow rate (about0.1 SCFM); air and cleaning solution temperature (ambient @21° C.). Thecleaning liquid was the same as in Example 1. The liquid flow ratesranged from 3 mL/min to 11.5 mL/min with 4 flow rate steps in betweenfor a total of six flow rates. The positions for photographs were:28-cm, 73-cm, 118-cm, 157-cm, and 207-cm. The flow map is shown in FIG.7 a.

At the 28-cm point, the single-rivulet mode is observed which continuesup to 8.5 mL/min liquid flow rate at which point it transitions to thefilm/foam mode. At the 73-cm point, the flow mode is single rivuletwhich continues up to 10.5 mL/min. At higher flow rates it transitionsto the film/foam mode. At the 118-cm point, the flow mode is RDF up to 5mL/min at which point the flow mode transitions to the single rivuletmode. This continues up to 10.5 mL/min at which point it transitions tothe film/foam mode. At the 157-cm point, the flow mode is asingle-rivulet flow. This continues up to 10.5 mL/min at which point ittransitions to the film/foam mode. At the 207-cm point, the flow mode isRDF up to 5 mL/min at which point the flow mode transitions to a singlerivulet mode. This continues up to 9.5 mL/min at which point ittransitions to the film/foam flow mode.

According to this flow mode map, the RDF mode is only occasionallyencountered and is not generally accessible under the above conditions.This is due the high hydrodynamic resistance of this narrow diametertubing. The air velocity is insufficient to induce instabilities leadingto formation of liquid fragments. Cleaning with rivulet flow under theseconditions is due solely to the meandering of the single-rivulet flowdue to transversal movement. To achieve optimal RDF flow a higherpressures and liquid and gas flow velocities are required as is shown inExample 7 below which was carried out at a gas pressure of 80 psi.

Example 7 Flow Regime Map for the 0.6 mm Tube @80 psi Air Pressure

The operating conditions were the same as in Example 6 but the airpressure was controlled at 80 psi which is the maximum rated pressurefor this very small diameter endoscope channel (elevator-wire channel).The results are given in FIG. 24.

At the 28-cm to 207 cm (i.e., over the entire length of the tube) theflow mode was RDF which continues up to about 10.5 mL/min at which pointit transitions to the single rivulet mode. The results of this exampledemonstrate that using higher air pressure and air velocity results inthe formation of the RDF even in the 0.6 mm channel which is favorablefor cleaning. This example is important since these dimensions aresimilar to the elevator-wire channels of flexible endoscopes.

Example 2-7 demonstrates that the operating conditions in terms of flowrates and gas pressure required to generate optimal RDF flow regimes forcleaning by rivulet flow depend strongly on the diameter of the tubingemployed and is different for different diameters. Since there is not asingle universal set of parameters for all channel diameters, optimalcleaning of multi-channel devices such as endoscopes requires that theconditions employed for each channel be optimized to produce the optimalflow mode, e.g., RDF in the case of rivulet flow.

Example 8 Examples of Liquid Cleaning Media Containing Single Surfactant

Liquid compositions containing single surfactants were prepared andtested by the flow mapping technique of Example 1 and flow regime mapsconstructed for endoscope tubes of different diameters (ID 0.6 mm to 6.0mm) as described in Examples 2-7. The compositions are summarized inTable 3. The air pressure range used in the evaluations was between 10to 30 psi and in other cases above 30 psi. The liquid flow rates used inthe evaluations were in the range defined by flow regime/mode mapssimilar to those given in Examples 2-7.

The surfactants belong to Class III as described above. The results fromall the experiments are summarized by an overall RDF rating and anoverall organic soil cleaning rating. All the surfactants providedcleaning media that formed the RDF flow regime in all the differentchannels and provided soil removal. However, the effectiveness in soilremoval varied somewhat. Organic soil removal was evaluated by theprocedure described in Example 15.

TABLE 3 Composition Ingredient B C E G H M Water 97.82 97.81 99.62199.67 99.67 99.37 SMS 0.13 0.13 0.13 0.13 0.13 0.13 STP 2.000 2.000 EDTA(39%) 0.15 0.15 0.15 0.15 AO-405 0.024 TERGITOL ® 0.050 1X PLURONIC ®0.060 0.050 0.050 L43 31R1 0.050 L62D 0.050 0.000 L81 0.025 Accusol 505N0.30 RDF Rating 3 3 n/a 3 3 n/a Organic Soil 4 2 n/a n/a n/a n/aCleaning Notes: RDF Rating: 1 to 5 scale where 1 = worst, 5 = BestOrganic Soil Cleaning: 1 to 5 scale where 1 = worst, 5 = Best; Ratingwas based on SEM acquired at 200X to 5000X magnification as in Example19

Example 9 Comparative examples of Liquid Cleaning Media ContainingUnsuitable Surfactant

The comparative examples listed in Table 4 were prepared and tested bythe identical procedure described in Example 8. However, the individualsurfactants belonged to either Class I (formed wetting films) or classII (formed excessive foam).

Comparative C-P employs a hydrotrope (xylene sulfonate) SX-40 which doesnot provides surface tension less than 55 dynes/cm which appears to beinsufficient to produce extensive fragmentation.

Comparatives C-Q and C-R were made with a castor-oil ethoxylate (15 EO),CO-15 and an acetylinic surfactant, SURFYNOL® 420 respectively bothproduced wetting films on the surface of endoscope channels. No rivuletsor liquid fragmentation were observed with Compositions Q and R nor wasthe RDF regime observed.

Comparative C-S and C-T were made with an alcohol ethoxylated, TERGITOL®TMN-10 and sodium lauryl sulfate (SLS) respectively. These surfactantshave a Ross-Miles foam height greater than 50 mm and produced thefoam/film regime which covered most of the channel cross-section andlength with er foam (generally) of film at low flow rates. The RDFregime was not observed under the conditions employed. Foamingsurfactants such as TMN-10 are not suitable for use in RDF cleaning ofendoscope channels or other luminal devices.

TABLE 4 Comparative Examples Ingredients C-P C-Q C-R C-S C-T Water 97.7797.82 97.82 97.82 97.77 SMS 0.13 0.13 0.13 0.13 0.13 STP 2.00 2.00 2.002.00 2.00 SX-40 0.10 CO-15 0.050 Surfynol 420 0.050 TMN-10 0.050 SDS/SLS0.10 RDF Rating 2 1 1 2 1 Organic Soil 1 2 2 3 3 Cleaning Notes: RDFRating: 1 to 5 scale where 1 = worst, 5 = Best Organic Soil Cleaning: 1to 5 scale where 1 = worst, 5 = Best; Rating was based on SEM acquiredat 200X to 5000X magnification as in Example 19.

Example 10 Examples of Liquid Cleaning Media Containing SurfactantMixtures

The examples listed in Table 5 were prepared and tested by the identicalprocedure described in Examples 8 and 9. In contrast to the previousexamples, the cleaning compositions contained a mixture of twosurfactants: an acetylinic surfactant, SURFYNOL® 485 and an alkoxylatedether amine oxide, AO-455. All the compositions performed well and someprovided very effective and robust RDF flow regimes.

TABLE 5 Examples Ingredients 10A 10B 10C 10E 10F 10G 10H 10I 10J Water97.80 97.79 99.63 97.51 97.510 97.510 97.510 99.360 97.38 SMS 0.13 0.1300.130 0.130 0.130 0.130 0.130 0.130 0.13 STP 2.00 2.00 1.00 1.00 1.001.00 2.00 TSPP 1.00 1.00 1.00 1.00 EDTA (39%) 0.150 0.150 SURFYNOL ®0.036 0.036 0.036 0.036 0.036 0.036 0.036 0.036 0.036 485 AO-455 0.0240.024 0.024 0.024 0.024 0.024 0.024 0.024 0.024 L61 0.025 0.025 L810.024 CP5 0.30 Accusol 455N 0.30 Accusol 460N 0.30 Accusol 505N 0.300.30 SX-40 0.40 RDF Rating 4 n/a 3 n/a n/a n/a n/a 4 n/a Organic Soil 3n/a n/a n/a n/a n/a n/a n/a n/a Cleaning Notes: RDF Rating: 1 to 5 scalewhere 1 = worst, 5 = Best Organic Soil Cleaning: 1 to 5 scale where 1 =worst, 5 = Best; Rating was based on SEM acquired at 200X to 5000Xmagnification as in Example 19

Example 11 Cleaning performance determined by Radionulcide Method (RNM)

This example compare the cleaning of endoscope channels with one phaseliquid flow and with RDF mode with the cleaning effectiveness assessedby the Radionulcide Method (RNM). RNM provides direct quantification ofcontaminants in the channels by counting the Gammaquanta/second/endoscope using a special Gamma camera (Picker, U.S.A.).This method does not require recovery of residual contamination from theendoscope, and thus provides accurate determination of cleaning level.Tc(99) in macroalbumen is mixed with the organic soil which is then usedto contaminate endoscope channels by injecting the mixture from one ofthe endoscope ports. Different channels can be tested separately. Imagesshowing the spatial distribution of contaminants before and aftercleaning are also acquired for each test.

A PENTAX® endoscope (Models EG-2901) was tested to determine theeffectiveness of liquid flow cleaning. 5 mL of Dry sheep blood was mixedwith 5 mL saline solution followed by adding 100 uM protamine sulfate.The desired dose of Tc-99 in macroalbumen was thoroughly mixed with theabove solution. 6.5 ml of the mixture was injected into the endoscopevia the A/W port located at the umbilical end of the endoscope followingthe contamination method of Alfa et al., American Journal of InfectionControl, 34 (9), 561-570 (2006). The endoscope was allowed to stand forat least one hour to allow blood clotting and adhesion to channel wallsto take place. Gamma-camera images were acquired at the following pointsduring the test: 1) right after contamination, 2) just before cleaning,3) after each step of pre-cleaning, cleaning, rinsing and drying. Ateach point, the quanta/second/endoscope was measured to determine theeffect of each segment of the cleaning cycle. Normal procedures wereused to determine and subtract radioactivity level arising fromaccidental spillage on the external surface of endoscope or the holdingtray.

In this test, summarized in Table 6 under the column labeled“Comparative 11”, the initial quanta/sec./endoscope (q/s/e) was 3407after 5 minutes of liquid flow cleaning of the air/water channel (1.4 mmID and about 350 cm in length) at a liquid flow rate of 7.5 mL/minute,the radioactivity decreased to 2603 q/s/e. After rinsing and drying, theradioactivity was further decreased to 1855 q/s/e. This exampledemonstrates that liquid flow cleaning does not effectively clean theA/W channel, as supported by the Gamma camera images given in FIG. 25.

The same PENTAX® endoscope as in the above comparative control wascontaminated with dry sheep blood and soiled as described above. Theinitial count before cleaning was 1044 q/s/e. This was reduced to 321q/s/e after an initial RDF pre-cleaning step. The residual soil levelwas further decreased to 59 q/s/e after RDF cleaning and rinsing. Theflow was injected from the A/W cylinder at the control handle ofendoscope. The experiment and results are described in Table 6 under thecolumn headed “Example 11”. The final residual radioactivity in theendoscope after cleaning with the RDF method was 59 q/s/e compared to1855 q/s/e when cleaning was done by liquid flow (Comparative 11).

TABLE 6 Steps Comparative 11 Example 11 Initial 3407 1044 Pre-cleaning3440 321 Liquid flow 2603 Rivulet-droplet flow 327 After rinsing anddrying 1855 59 Rivulet-droplet flow advantage 262 Pentax Endoscope ModelEG-2901 EG-2901 Soil (see footnote) PB2 PB2 Air Pressure (psi) 0 28Liquid flow rate (ml/min) 75 15 Pre-cleaning time (min) 2.5 2.5 Liquidflow time (min) 2.5 0.0 Rivulet-droplet flow cleaning time 0.0 2.5 (min)Two-phase rinsing time (min) 3.0 3.0 Drying time (min) 2.0 2.0 Note:PB2: 5.0 ml dry sheep blood, 5.0 ml saline, 100 μm potamine sulfate andradioactivity material that makes about 11.5 ml of soil.

Further studies have demonstrated that a significant portion of theresidual radioactivity in Example 11 is due to one or more hot spotsarising from contaminating port.

High-sensitivity images (FIG. 25) comparing endoscopes cleaned by liquidflow (FIG. 25 a) and with cleaning using Rivulet Droplet Flow (FIG. 25b) demonstrate the highly effective cleaning of the surface of thechannel by the method of the invention.

Example 12 RDF Cleaning of Air/Water (A/W) Channel Soiled with ClottedBlood

In this series of tests, the soil was based on clotted fresh sheep bloodwhose formula is given under Table 7 below. Blood contamination ofendoscopes is very common and is considered to be a tough soil to cleanwith liquid flow methods. 6.5 mL of the clotting mixture including Tc-99isotope was injected into the A/W channel from the umbilical end of theendoscope. Six tests were made where cleaning was performed at 28 or 14psi air and with liquid flow rate of 15 mL/min or 7.5 ml/min. Theseoperating conditions were selected by the flow mapping method describedabove to give the RDF flow regime. The test cleaning compositionincluded an alkaline surfactant solution based on 0.0.05% nonionicsurface Tergitol (1×) at a pH of about 10.0. The cleaning solution andair were injected from the A/W cylinder located in the control handle ofthe endoscope (PENTAX® EG-3401).

The results of Test 1 to 6 summarized in Table 7 indicates that the RDFflow regime at air pressures 14-28 psi and liquid flow rates between 7to 15 ml/min was able to decrease the radioactivity in the endoscope tolevels that can be considered “clean” according to published reports(Schrimm et al., Zentr. Steril. 2 (5), 313-324 (1994). For a smallhand-held medical device, if the residual radioactivity after cleaningis in the range of 6 quanta/second/device the device is considered“clean” and is presumed to be equivalent to about 10E6 (“6 log”)reduction in the number of organisms. In the case of large endoscopessuch as PENTAX® (EG-3401), the residual q/s/e were: 0, 6, 36, 41, 75 and99 (Table 7). These levels indicate that the RDF method is effective inproducing “clean” endoscopes since the endoscope is 10 times larger thanthe hand-held devices used in the published data. The RDF providedcleaning advantage estimated between 176 to 543 q/s/e compared to thelevel achieved after pre-cleaning step which is assumed to be equivalentto liquid flow only cleaning. The differences between the RDF cleaningadvantage in the various tests is due to the different levels of initialcontamination and other variable parameters used in the testing.

TABLE 7 Steps Test 1 Test 2 Test 3 Test 4 Test 5 Test 6 Initial 26443957 2982 4524 5321 3115 Pre-cleaning 237 217 312 493 549 392 Aftertwo-phase rinsing and 0 41 36 99 6 75 drying Rivulet-droplet flow 237176 276 394 543 317 advantage Pentax Endoscope Model EG-3401 Soil (seefootnote) PB1 PB1 PB1 PB1 PB1 PB1 Air Pressure (psi) 28 28 14 28 14 28Liquid flow rate (ml/min) 15 15 7.5 15 7.5 15 Pre-cleaning time (min)2.5 2.5 2.5 2.5 2.5 2.5 Liquid flow time (min) 0.0 0.0 0.0 0.0 0.0 0.0Rivulet-droplet flow cleaning 2.5 2.5 2.5 2.5 2.5 2.5 time (min)Two-phase rinsing time 3.0 3.0 3.0 3.0 3.0 3.0 (min) Drying time (min)2.0 2.0 2.0 2.0 2.0 2.0 Note: PB1: 2.5 mL pure fresh sheep blood, 2.5 mLsaline, 100 μm protamine sulfate and radioactivity material that makesabout 6.5 mL of soil.

Example 13 Bioburden Removal as Function of Flow Mode at Three Pressures

This example demonstrates how flow modes in endoscope channels affectthe cleaning efficacy as determined by testing Recoverable Bioburden(microorganisms) following an accepted recovery protocol. Anotherobjective was to define the effect of air pressure (velocity) and liquidflow rate on the flow regime and on the effectiveness of removingbioburden form actual endoscopes channels.

The Artificial Testing Soil (ATS) developed by Alfa is now accepted as asimulant for worst-case organic soil found in patient endoscopes aftergastrointestinal procedures (U.S. Pat. No. 6,447,990). The detailedprotocol for testing the effectiveness of cleaning endoscopes waspublished by Alfa et al., American Journal of Infection Control, 34 (9),561-570 (2006), including the citations therein. The basis of the Alfacleaning evaluation includes contaminating endoscope channels with asufficient volume of a high-count inoculum (normally>8 log 10 cfu/ml)using a cocktail comprising three organisms covering a representativespecies from Gram positive, Gram negative and yeast/fungus mixed in theATS soil. Depending on length and diameter, each channel normallyreceives 30 to 50 ml/channel of the ATS soil-bioburden mixture and thenis allowed to stand for two hours to simulate the recommended practiceused in reprocessing endoscopes. This contamination procedure isspecific and requires special skill to ensure that each channel receivesa complete coverage with ATS soil and organisms. After a waiting time,the endoscope channels is lightly purged with a know volume of air usinga syringe to remove excess mixture form the channels. The endoscope isthen transferred to the cleaning device for evaluation. At theconclusion of the cleaning and rinsing cycles (including exteriorcleaning), residual bioburden in the channel is recovered according to aspecific and precise protocol.

The accepted bioburden recovery method from the working channels(suction and biopsy) is to use the Flush/Brush/Flush (F/B/F) protocolfor the working channels and the Flush/Flush (F/F) for the narrow A/Wchannels. The validated F/B/F protocol requires first flushing theentire channel with a sterile reverse osmosis (sRO) water andquantitatively collecting the recovered solution of this step in asterile vial. The second step requires brushing the entire channel witha specially-designed endoscope brush multiple times using a specificsequence and manipulation to reach the entire surface of the channel andto dislodge the attached organism in a quantitative and reproduciblemanner. The brush tip is then cut off and placed in the same collectingsterile vial. A third bioburden recovery step involves another flushingof the channel with sRO water to remove the organisms detached by thebrushing action as described above. The flushing liquid of this step isadded to the same collection vial. The total volume of liquid recoveredis maintained at about 40 mL. The contents of the vial are thensonicated to dislodge organisms from the brush or to suspend aggregatedbacteria recovered. An aliquot of this recovered fluid is plate culturedas described by Alfa et al., referenced above. Serial dilution practiceis used to produce reliable results following strict microbiologylaboratory practices and routines. Three replicates are made in eachtest. The recovered bioburden from the suction/biopsy channel is termedL1. Intimate knowledge of the endoscope and its channel configuration isnecessary to perform this protocol.

Recovery of bioburden from the Air/Water (A/W) narrow channels (ID 1.0to 2.1 mm) is normally performed with the Flush/Flush (F/F) protocolwhich does not include the brushing step. These narrow endoscopechannels cannot be bushed due to their small diameter and to the complexconfiguration of endsocopes, and there are no available brushes that canbe perform this operation. However, the F/F protocol has been validatedto produce excellent recovery for the A/W channel. At the conclusion ofthe cleaning and rinsing cycles, residual bioburden is recovered with adouble flushing method using sRO water according to the Alfa protocol.The recovered liquid is collected from both air and water channels andpooled together in one sterile vial. Approximately 30 mLs are collectedand subjected to the same preparation and culturing procedures describedabove. The recovered bioburden from the Air/Water channel is termed L2.

In each test the inoculum is cultured according the accepted protocolsand the results expressed in colony forming units per mL, or simplycfu/mL. Generally, the recovered bioburden from the channel aftercleaning is expressed as cfu/mL. The product of cfu/mL and volume of therecovered liquid from each channel in mLs yields total cfu/channel. Whenthe latter value is divided by the surface area of the channel in cm2,bioburden surface density can be expressed in cfu/cm2. Since the volumeof the liquid recovered from the channel is more or less the same as thevolume of inoculum used to contaminate the channel, the log 10 removal(reduction) factor (RF) can be obtained by subtracting the log 10 ofcfu/mL of recovered solution form the log 10 cfu/mL of the inoculumused. This calculation may be some what approximate since a positivecontrol of a contaminated endoscope (not cleaned) need to be recoveredat the same time to arrive at the actual RF. However, according to ourexperience with many tests the two methods for estimating RF are closeto each other within +/−0.5-1.0 log. Negative controls are used in eachtest according to the Alfa protocol.

In this example, we assessed the cleaning of endoscope channels usingEnterococcus faecalis ATCC 29212. Enterococcus faecalis is agram-positive opportunistic pathogen known to form biofilms in vitro.This species is known to possess strong adhesion to endoscope channelsand is considered an excellent surrogate worst case organism to reliablyassess the cleaning effectiveness.

To demonstrate the effect of flow modes on the effectiveness of removingbioburden according to method of this invention, we selected three airpressures namely: namely 10, 28, and 55 psig. At each air pressure, wetested the cleaning effectiveness at three liquid flow rates. The liquidflow rates used to assess the cleaning of the suction/biopsy channel(ID=3.7 mm; length=400 cm max) are shown in Table 8. The liquid flowrates used to assess the cleaning effectiveness of the A/W (ID=about 1.6mm; length=400 cm max) channels are shown in Table 8. The range ofliquid flow rates was chosen by constructing a flow regime map accordingto the methods described in Example 1-7 for the particular endoscopechannels employed and selecting the controlling parameters set forthabove that provided RDF flow regime. The maps used in this case arethose described in Example 2—FIG. 26 b for the 2.8 mm tube and Example3—FIG. 26 a for the 1.8 mm tube. The low liquid flow rate was selectedwhere the flow regime is described as dry/sparse over most of thechannel length and when the amount of surface flow entities on thechannel surface is small. The intermediate liquid flow rate was selectedto represent nearly optimal RDF regime with intense rivulet meanderingand fragmentation with large amount of moving liquid entities havingthree-phase contact line. The higher liquid flow rate was chosen suchthat the flow regime is in the film/foam regime where the surface of thechannel is covered by a complete film with some foam and with littleopportunity to form liquid entities.

Table 9 summarizes the results of nine tests to assess bioburden removalat three flow modes at three air pressures. At each pressure, the liquidflow rate determines the flow mode that can be obtained at the operatingconditions. Examples of large (S/B) and narrow (A/W) channels weretested. The cleaning composition used was Composition 10A in Table 5,where the surfactant mixture was found to give excellent RDF mode whenused at appropriate operating conditions. The injection of air andliquid into the endoscope was made according to the sequencing scheme Adescribed in Example 16 where the flow is injected from the controlhandle following the cycle described here.

At 10 psig air pressure (Table 8), Test No. 2 represents near optimalliquid flow rate where the most of the channel is covered with elementsof the RDF mode including rivulets, meandering rivulets and liquidfragments/entities covering the most of the channel length and surface.Test No. 2 results show the best bioburden removal from both S/B (L1)and A/W (L2) channels with RF values of 6.047 and 6.472, respectively.In this test, residual/recoverable organisms after RDF cleaning wereonly 48 cfu/cm2 and 17 cfu/cm2 form the S/B and A/W, respectively. Atlower liquid flow rates where the treatment number is small due to thefew number of surface flow entities formed under these conditions (TestNo. 1), the results are worse. At higher liquid flow rate where most ofthe surface is in the film/foam regime and the cleaning with liquidentities is not possible (Test No. 3) the results were also worsecompared to those of Test No. 2. Overall, the cleaning effectivenessdemonstrates the significance of using the RDF mode (Table 8),especially in the S/B channel (L1). OLYMPUS® Colonoscopes (model CF TypeQ160L) were used to simulate the worst case conditions especially forvery long channels.

TABLE 8 Liquid Air Flow Inoculum Recoverable Bioburden Test PressureRate (Log10 (Log10 Reduction No. (psig) (ml/min) cfu/ml) (cfu/ml)cfu/ml) (cfu/cm2) Factor L1 - Suction/Biopsy (Flush/Brush/Flush) 1 105.00 8.439 7830 3.893 787 4.546 2 10 22.5 8.710 460 2.663 48 6.047 3 1067.50 8.393 1830 3.262 171 5.131 4 28 5.00 8.369 6400 3.806 605 4.563 528 22.50 8.572 173 2.238 16 6.334 6 28 67.50 8.560 1700 3.230 151 5.3307 55 5.00 8.423 1390 3.143 135 5.280 8 55 22.50 8.423 497 2.696 56 5.7279 55 67.50 8.710 460 2.663 40 6.047 L2 - Air/Water (Flush/Flush) 1 101.75 8.439 6830 3.834 607 4.605 2 10 5.75 8.710 173 2.238 17 6.472 3 1016.80 8.393 190 2.279 14 6.114 4 28 1.75 8.369 293 2.467 17 5.902 5 285.75 8.572 150 2.176 8 6.396 6 28 16.80 8.560 1780 3.250 129 5.310 7 551.75 8.423 52300 4.718 3597 3.705 8 55 5.75 8.423 70 1.845 4 6.578 9 5516.80 8.710 57 1.754 3 6.956

The same trend is found at 28 psig air pressure (Table 8) where theregion corresponding to near optimal RDF mode gives the best result(Test No. 5). Low liquid flow rates (Test No. 4) corresponds to thesparse/dry flow mode with small treatment number and the high flow rateproduced the foam/film regime (Test No. 6). Test No. 5 corresponds tothe best results for both S/B and A/W channels as supported by the verylow recoverable cfu/cm2 and high RF values. Again, cleaning in the RDFmode is demonstrated to give the best results at the 28 psig airpressure; RF values higher than 6.0 could be achieved under theseconditions.

At even higher air pressures (55 psig), the main trend remains in thatwhen the RDF and higher treatment number can be achieved within the 300seconds cleaning yet better cleaning is possible. At this high pressure,the liquid flow rate optimal for the RDF mode appears to shift to highervalues because of the high gas velocity obtained at this pressure.

The RF for optimal manual cleaning of endoscope channels has beenestablished by Alfa et al. at 4.32+/−1.03 (Alfa et al., American Journalof Infection Control, 34 (9), 561-570 (2006)). Also, industry estimatesRF of manual cleaning of endoscopes in the field about 1-4 or about 3.0on the average. The manual cleaning results are based on followingprotocols for manual cleaning recommended which include brushing of theworking S/B channels and flushing the A/W (protocol provided in Alfa etal., cited above). The optimal RF value obtained with the RDF cleaningat 10 and 28 psig air pressure is between 6.047 and 6.472 which issignificantly better than the best manual cleaning results reported byAlfa et al by about 2 log 10. Based on these results, the RDF cleaningprovides significantly better results than manual cleaning withbrushing.

Example 14 Bioburden Removal with the RDF Mode Using Multiple Organisms

The three bacterial strains used for this example were Enterococcusfaecalis ATCC 29212, pseudomonas aeroginosa ATCC 27853 and candidaalbicans ATCC 14053. This example follows the methods and protocolsdescribed in Alfa et al. and the references cited therein. Endoscopechannels were contaminated with the ATS including cocktail of the threeorganisms as described in Example 13. OLYMPUS® Colonoscopes (model CFType Q160L) were used to simulate the worst case conditions especiallyfor very long channels. Both S/B and A/W channels were tested and theresults are summarized in Table 10. The cleaning/rinsing cycles weresame as in Example 13. Composition 10A in Table 5 was used as thecleaning liquid. The operating conditions including: air pressure,liquid flow rate and ports of injection were selected to provide optimalor near optimal RDF for the channel sizes present in endoscope used.Flow mode maps similar to those of Example 2-7 were used to define theRDF mode and to select the operating conditions. All tests were made at28 psig air pressure.

RF values for Ten (10) independent tests regarding the cleaning S/Bchannel (L1) were as follows: 1) Enterococcus faecalis 5.60 (±0.82); 2)pseudomonas aeroginosa 7.02 (±1.38); 3) candida albicans 5.32 (±0.56).These results are significantly better than the best manual cleaningwith brushing as per Alfa et al., and are far superior to published databy Zuhlsdorf (cited in Alfa's paper) where cleaning is performedaccording other AERs based of liquid flow cleaning methods. The mainconclusion of the present example is that cleaning endoscope channelswith the RDF mode achieves reliable and robust high-level cleaningbetter than manual brushing or other methods when the threerepresentative organisms were used in the evaluation.

The RF values obtained in cleaning A/W channels (L2) of the sameendoscope were as follows: 1) Enterococcus faecalis 5.76 (±1.01); 2)pseudomonas aeroginosa 6.92 (±1.02) and 3) candida albicans 5.82(±0.94). These results are significantly better than the best manualcleaning values published by Alfa et al., or published data by zuhlsdorfet al. Comparing the results of this example with published dataindicated that the RDF mode provides a clear advantage in cleaning verynarrow channels compared to other methods as supported by the RF valueobtained in the A/W (L2) case.

TABLE 9 E. faecalis P. aeruginosa C. albicans Inoculum Inoculum InoculumTest Endoscope (Log10 (Log10 (Log10 No. Model cfu/ml) R.F. cfu/ml) R.F.cfu/ml) R.F. L1 - Suction/Biopsy (Flush/Brush/Flush)  1 PENTAX ® 8.495.04 7.44 7.36 8.06 5.01 EG-2910  2^(a) PENTAX ® 8.45 4.79 7.79 7.798.02 5.31 EG-2910  3^(b) PENTAX ® 8.30 6.62 8.03 8.03 7.86 5.73 EG-2910 4c PENTAX ® 8.71 5.78 8.27 8.13 7.44 4.82 EG-2910  5^(d) PENTAX ® 8.716.12 8.27 8.13 7.44 5.02 EG-2910  6^(e) PENTAX ® 8.51 5.28 7.70 5.627.94 5.30 EG-2910  7^(f) PENTAX ® 8.60 7.03 8.22 8.22 7.84 6.49 EG-2910 8^(g) OLYMPUS ® 8.30 4.71 8.28 4.56 7.18 4.84 CF-Q160L  9^(h) OLYMPUS ®8.38 4.75 8.48 5.15 7.28 4.78 CF-Q160L 10^(i) OLYMPUS ® 8.23 5.10 8.917.20 7.90 5.86 CF-Q160L 11^(j) OLYMPUS ® 8.57 6.33 CF-Q160L Average:8.48 5.60 8.14 7.02 7.70 5.32 Standard 0.16 0.82 0.42 1.38 0.33 0.56Deviation: L2 - Air/Water (Flush/Flush)  1 PENTAX ® 8.49 4.64 7.44 5.438.06 5.33 EG-2910  2^(a) PENTAX ® 8.45 4.66 7.79 7.46 8.02 6.06 EG-2910 3^(b) PENTAX ® 8.30 5.89 8.03 7.41 7.86 5.73 EG-2910  4c PENTAX ® 8.716.02 8.27 8.22 7.44 4.94 EG-2910  5^(d) PENTAX ® 8.71 6.30 8.27 6.847.44 5.37 EG-2910  6^(e) PENTAX ® 8.51 4.58 7.70 6.10 7.94 5.78 EG-2910 7^(f) PENTAX ® 8.60 7.71 8.22 8.22 7.84 7.80 EG-2910  8^(g) OLYMPUS ®8.30 5.59 8.28 6.12 7.18 5.14 CF-Q160L  9^(h) OLYMPUS ® 8.38 4.88 8.485.72 7.28 4.98 CF-Q160L 10^(i) OLYMPUS ® 8.23 6.71 8.91 7.65 7.90 7.07CF-Q160L 11^(j) OLYMPUS ® 8.57 6.40 CF-Q160L Average: 8.48 5.76 8.146.92 7.70 5.82 Standard 0.16 1.01 0.42 1.02 0.33 0.94 Deviation: Notes^(a)Two RDF cycles ^(b)No water filter/cold water/2 hr. drying time(March 2005) cWith water filter/cold water ^(d)Without water filter/coldwater ^(e)Flush/Brush/Flush Method of Recovery (July 2005) ^(f)Hot tapwater (September 2005) ^(g)Cold tap water (April 2008) ^(h)Cold RO water(April 2008) ^(i)Cold RO water with continuous rinse (May 2008) ^(j)10Tap water with continuous rinse (September 2008)

Example 15 Cleaning of Organic Soils from Endoscopes with RDF FlowRegime

One criteria cleaning effectiveness used in the pharmaceutical industryis based on measuring the level of organic soil removal from surfaces ofequipment and devices. Transfer of contamination from one drug toanother due to the use of the same equipment can lead to seriousconsequences which requires adhering to cleaning protocols approved byFDA. To apply these principles, two artificial soils, red soil (ISO15883-5 Annex R) and black soil (ISO 15883-5 Annex P), were chosen tosimulate patient soils encountered during various endoscopic procedures.These two soils were used to contaminate the endoscopes by applying thesoil and allowing it to dry for at least one hour following application.

The commercial endoscopes tested were OLYMPUS® TJF-160VF duodenoscopeand a PENTAX® ED-3470 duodenoscope. These endoscopes were chosen torepresent some of the most difficult challenges for the cleaning system,with lumens ranging from 0.8-mm to 4.2-mm ID, and a total length inexcess of three meters. Endoscope cleaning was performed using theapparatus described in Example 1 and shown diagrammatically in FIG. 23.

The cleaning efficacy was evaluated by testing water extracts from thecleaned lumens for residual total organic carbon (TOC) and protein. Thefollowing protocol was employed. Endoscope lumens were contaminated withblack or red soils at a level given within Table 10. Contaminationlevels were based on recommendations contained within “Worst-casesoiling levels for patient-used flexible endoscopes before and aftercleaning,” published by Michelle Alfa et al., in Amer. J. Infect.Control. 27:392-401, 1999. Total lumen lengths and internal diameterslisted in the table were used to calculate total surface area. Cleaningtests included a 5-min cleaning cycle and 5-min rinse cycle withfiltered tap water.

TABLE 10 Lumen Test Conditions Length ID Dose Endoscope Channel (mm)(mm) Soil (ml) Trials OLYMPUS ® Suction/ 3048 4.2 Control 0.0 3TJF-160VF Biopsy Air/Water 3048 2.7 Control 0.0 3 Elevator Wire 1537 0.9Control 0.0 3 Suction/ 3048 4.2 Black 6.5 3 Biopsy Air/Water 3048 2.7Red 1.0 3 Elevator Wire 1537 0.9 Red 0.18 3 PENTAX ® Suction/ 3105 4.2Control 0.0 3 ED-3470 Biopsy Air/Water 3105 2.5 Control 0.0 3 Suction/3105 4.2 Black 6.6 3 Biopsy Air/Water 3105 2.5 Red 1.0 3 OLYMPUS ®Suction/ 3048 4.2 Control 0.0 1 TJF-160VF Biopsy Air/Water 3048 2.7Control 0.0 1 Suction/ 3048 4.2 Black 6.5 3 Biopsy Air/Water 3048 2.7Red 1.0 3 PENTAX ® Suction/ 3105 4.2 Control 0.0 1 ED-3470 BiopsyAir/Water 3105 2.5 Control 0.0 1 Suction/ 3105 4.2 Black 6.6 3 BiopsyAir/Water 3105 2.5 Red 1.0 3

Three method controls (blanks) were performed in every test. Theseblanks were subjected to the RDF cleaning process (5-min) and rinsingwith distilled water (5-min) prior to extraction of residual organicsoil. Extraction was performed using deionized water and lumens withlarger lumen dimensions (>1.6-mm) were brushed with lumen brushes per avalidated method. Extracts were collected in clean glass vials and wereanalyzed for total organic carbon (TOC) and protein residues. Totalorganic carbon was determined using a Total Organic Carbon (TOC)analyzer model 1010 from OI Analytical, while protein was determinedusing a Fluorescence Spectrophotometer model RF 5301 from Shimadzuaccording to standard methods. The operational parameters included: 1)Air pressure for all lumens 28 psig; 2) Cleaning liquid: Composition 10Ain Table 5; 3) Liquid flow rates as per flow mode maps and Example 2-7.Black soil was introduced into the biopsy port near the control handlearea of the endoscopes using a syringe. Black soil was introduced intothe suction port located at umbilical end of the endoscopes. Red soilwas injected into the air/water channel port located at the umbilicalend of the endoscopes. All soils were well distributed into theirrespective channels with multiple injections of air. Table 11 belowdetails extractable residues recovered from endoscope lumens.

TABLE 11 Protein and TOC Residues Following RDF Cleaning of SoiledLumens Protein TOC Endoscope Channel (μg/cm²) (μg/cm²) OLYMPUS ®Suction/ ND, ND, 0.02 0.06, 0.04, 0.05 TJF-160VF Biopsy Air/Water 0.02,ND, ND 0.05, ND, ND Elevator Wire 0.97, 0.46, 1.40 2.44, 1.17, 3.36PENTAX ® Suction/ ND, 0.19, 0.04 ND, 0.15, 0.09 ED-3470 Biopsy Air/Water0.08, 0.04, ND 0.23, 0.06, ND OLYMPUS ® Suction/ 0.04, 0.12, ND 0.09,0.03, ND TJF-160VF Biopsy Air/Water ND, ND, ND 0.01, ND, ND PENTAX ®Suction/ ND, ND, 0.10 ND, ND, ND ED-3470 Biopsy Air/Water 0.08, 0.14, ND0.23, 0.25, ND ND = Non-Detect/Below the Limit of Detection

The results of this example demonstrate that RDF cleaning providedexcellent cleaning capability for suction/biopsy and air/water channelsof two commercially available endoscopes representing the range ofstandard lumen challenges. The RDF method also provided adequatecleaning capability for the elevator-wire channel of the OLYMPUS®TJF-160VF. These experiments demonstrate that the RDF method achieveshigh level removal organic soils recommended for testing endoscopes.This also confirms that RDF can meet and exceed the 6.2 ug/cm2 cleaningcriteria set by Alfa et al for organic soils cleaning. These results aresignificantly better that liquid cleaning methods reported by Alfa etal. The above tests were repeated using ATS soil with similar results asin Table 11.

Example 16 Devices for Flow Sequencing for Cleaning Endoscopes

This example illustrates devices to produce two flow sequences used forapplying rivulet-droplet flow (RDF) and for discharging waste liquidsduring reprocessing. The two flow sequences are discussed below:

Scheme A. RDF cleaning through handle ports of the endoscope—Customfabricated adapters are used to connect the endoscope internal channelsto the fluid distribution manifold. The rivulet-droplet flow isintroduced using two main flow paths: i) the first flow path isdedicated to the suction control port V3 and the biopsy channel inletV1, and ii) the second flow path directs the RDF into the air-waterfeeding valve V2. Two separate single flow paths are dedicated to theforward water jet port V6 and elevator wire channel V7, as shown in FIG.16 a. To enhance the cleaning for the air/water channel, V4 is closedduring one step of cleaning, thus forcing all the RDF directly towardsthe distal end.

Scheme B. TPF cleaning connected to the umbilical end—A second flow pathis designed to introduce the RDF to the suction port and air/water inletport at the umbilical end. RDF is introduced using two main flow paths:i) the first flow path is dedicated to the suction port Vb and thebiopsy channel inlet Vc, and ii) the second flow path directs the fluidinto the air/water inlet Va. Exhaust fluids during reprocessing stepsare discharged from the distal end, air/water feeder valve Vd, andsuction control valve Ve, as shown in FIG. 16 b. Each cleaning step isassociated with an ON and OFF cycle to ensure that the dead spaces inthe biopsy channel inlet, air/water feeder valve and suction controlvalve are cleaned and rinsed. In the “ON” cycle, valves Vc, Vd and Veare open. In the “OFF” cycle, these valves are closed. Cleaning can alsobe performed with both Vd and Ve closed.

Example 17 Determination of Treatment Number of Water

Analysis of high-speed images reveals that there is usually rivuletmeandering and that such meandering mainly provides treatment of theinlet portion of tube. Sub-rivulets and sub-rivulets fragments (variouscylindrical bodies, and droplets) are seen on the bottom of tube whenthis is not covered by the rivulet at certain moment. A set of slidingflow entities provides additional cleaning of the bottom half of tube.

Equation 5 (below) can be used to quantify treatment number of the upperhalf of tube because variations in the subrivulet fragment diameter areusually small for the images obtained at 30 psi air pressure and at arange of liquid flow rates. As a consequence, the variation in slidingvelocity is not large as well because the sliding velocity depends onthe fragment diameter, while its dependence on fragment length isweaker. Taking altogether into account, 5 takes form for treatmentnumber by subrivulet fragmentsNT _(rf)=2t _(cl) d _(av) ^(rf) U _(av) ^(rf) N _(av) ^(rf) /S  (27)where N_(av) ^(rf) is the averaged number of subrivulet fragments perimage, U_(av) ^(rf) is the average velocity of the fragment, t_(cl) isthe cleaning time (time over which the experiment was carried out) andd_(av) ^(rf) is the average diameter of the rivulet fragment observed.Since only the upper half of tube is inspected, the multiplier 2 appearsbecause S/2 is used instead of S, where S is the area of tube section ofthe visual area under microscope at the magnification used.

Treatment Number of Pure Water: This example illustrates a method forcalculating the treatment number (NT) based on image analysis for thecase of pure water. A tube with diameter 2.8 mm, length 200 cm wasexamined at 30 psi air pressure and water flow rate 20 mL/min. Imageswere obtained at 3 positions along tube length correspondingapproximately to the beginning, middle and end of the tube. At thebeginning of tube (28-cm position) there was no meandering. The bottomrivulet was well visible and occupied the entire bottom of tube.Meandering rivulet was visible at the middle (118-cm position) and atthe end (208-cm position). The meandering occurs mainly across the lowerhalf of tube. The rivulet is seen either in the bottom middle, leftside, or right side of the tube.

In the case of water, sub-rivulets were present on 2 among 8 images attube middle. No sub-rivulets were present on 8 images at tube end.Sub-rivulet fragments were present at the middle and the end of thetube. These sub-rivulet fragments were almost of the same diameter,about 100 um, while their length varies within a broad range.

The diameter of droplets was approximately one half of the diameter ofsub-rivulet fragments, namely about 50 micron. The averaged values forthe number of sub-rivulet fragments and droplets per image at the middleand end viewing areas of the tube are collected in Table 12.

TABLE 12 Tube section N_(av) ^(rf) N_(av) ^(dr) Middle 6 2 End 6 2

For tube with diameter 2.8 mm, S=0.7 cm² per image. The substitution ofthese values and treatment time t_(cl)=300 seconds into Eq 15 yields thefollowing treatment numbers arising for rivulet fragments and droplets:Middle Section:NT _(av)=800(6·10⁻² U _(av) ^(rf)+10⁻² U _(av)^(dr))  (28)End Sectuion:NT _(av)=800(6·10⁻² U _(av) ^(rf)+10⁻² U _(av) ^(dr))  (29)

This yields NT_(av) for rivulet fragments of 48.U_(av). The NT term fordroplets in this example is very small and can be ignored.

If the sub-rivulet cross section does not change along and its axis, itis straight and moves along tube axis, its role in cleaning isnegligible. However, the sub-rivulet cross section was found to changemore than about twice per image. Apart from weak meandering, no largekinks in its shape were found in the sub-rivulets. Taking into accountabout 4 kinks or meandering waves per images and the presence of widersection in the sub-rivulets, the treatment by sub-rivulet may beestimated with d_(av) ^(sub)˜3.4·10⁻² cm, while N_(av) ^(sub)=0.25. Thisyields:NT _(sub)=800·3·10⁻² U _(av) ^(sub)=24U _(av) ^(sub)  (30)

The sum of NT terms for rivulet fragments (rf), droplets (dr) andsub-rivulets (sub) yields total treatment number for water. In order tocompute the above terms, the sliding velocity of the correspondingsurface flow elements (rf, dr and sub) must be known. The averagevelocity of was found to 7 cm/sec for rivulet fragments, 4 cm/sec fordroplets and 0.7 cm/sec for sub-rivulets. Substitution of these valuesfor the sliding velocity of the appropriate surface flow entity gives anoverall Treatment Number for water of 385 in this experiment, i.e., thechannel are viewed is swept 385 times during the 300 second cleaningtime.

Example 18 Influence of Surfactants on Treatment Number

Many surfactants were tested to assess their influence on sub-rivuletformation and further fragmentation to other surface flow entities andon treatment number. The measurement technique and analysis was similarto that described in Example 16. The conditions employed were: Tubing:2.8 mm ID, 2 m long; Air Pressure: 30 psig; Liquid Flow Rate: 19.6ml/min; Treatment Time: 300 sec. All the surfactant solutions (liquidcleaning medium) included: sodium metasilicate (1.3%); sodiumtriphosphate (SPT) (8.7%) and tetrasodium pyrophosphate (2.0%) and wereprepared with deionized water.

The results are summarized in Table 13. The measured sliding velocitiesfor the surface flow elements used to calculate the Treatment Numbersaccording to Eq 5 are Rivulet Fragments—7 cm/sec; Droplets—4 cm/sec;Sub-Rivulets—0.7 cm/sec

TABLE 13 Rivulet Overall Fragments Droplets Sub-rivulets Treatment Conc.(rf) (dr) (sub) Number ( Liquid/Surfactant (%) NT_(rf) (a) NT_(dr) (a)NT_(sub) (a) ΣNT Pure Water 336 32 17 385 Tallow amine 2EO 0.05 392 1510 417 ethoxylate (Surfonic T-2) EO-PEO copolymer- 0.05 266 92 175 533HLB = 10.5 (Pluronic L43) Octyl sulfate 0.05 504 32 17 553 (NAS-8)Tallow amine 5 EO 0.05 490 208 17 715 ethoxylate (Surfonic T-5)Butyl-terminated 0.1 560 131 245 936 C12 alcohol ethoxylate (DehyponLT-54) Tallow amine 15EO 0.05 700 248 20 968 ethoxylate (Surfonic T-15)Acetelynic 0.036 + 0.024 1260 512 20 1792 ethoxylate (HLB 17) (Surfynol485) + Alkoxylated ether amine oxide (AO-455)

Inspection of Table 13 indicates that the tallow amine 2EO ethoxylate(Surfonic T-2) which has a low HLB and is insoluble tends to formannular films (receding contact angle close to or equal to water) andprovides a Treatment Number again comparable to water. Increasing thedegree of ethoxylation to 5EO increases the Treatment Number somewhatwhile an increase in ethoxylation to 15 EO (Surfonic T-15) provides amuch more effective cleaning medium exhibiting a 2.5 fold increase inTreatment Number.

It should be noted that the concentration of surfactant employed is alsoimportant parameter governing its ability to generate an optimal flowregime. For example, the Tallow 15 EO ethoxylated (Surfonic T-15) usedin this experiment was 0.05%. However, when the concentration isincreased to 0.1% the solution generates significant foam and theTreatment Number is found to decrease.

Table 14 also demonstrates mixed surfactant system composed of theAcetelynic ethoxylate (Surfynol 485) and the Alkoxylated ether amineoxide (AO-455) provides provides vastly increased Treatment Number thatis 4.6 time more effective than water.

These results indicates that the proper selection of the surfactant andits concentration so as to meet the surface tension, wetting and foamingrequirements described above is critical to its performance in thecleaning method of embodiments of the present invention.

Example 19 Channel Cleaning with Discontinuous Plug Droplet Flow (DPDF)

To test the cleaning effectiveness of the Discontinuous Plug DropletFlow flow regime (DPDF), we performed cleaning experiments using 2.8 mmdiameter Teflon channel (2 meter long) contaminated with the black soilas described in Example 15. After contamination the channel was allowedto dry in the channel for 24 hour before cleaning. The cleaningconditions used were: 28 psig air; 19.6 mL/min liquid flow; cleaningliquid included Surynol 485 and AO-455 (designated Composition 10A inTable 5); treatment time 300 seconds; air and liquid used @ roomtemperature.

The cleaning procedure was based on introducing the cleaning liquid intothe channel for 2-3 seconds without air and then introducing the air for6 seconds. This mode of cleaning first resulted in creating a movingmeniscus that swept the entire perimeter of the channel from the inletto outlet. Almost concurrently, introducing the air transformed thecleaning liquid into surface flow entities including rivulets,sub-rivulets, rivulet fragments and droplets which covered the entiresurface of channel during a portion of the time. The latter part of theair pulse resulted in complete dewetting and drying of the surface ofthe channel. The channel becomes ready to receive effective cleaningwith the moving contact line during the next step. The above cleaningstep was repeated for the 300 seconds or about 43 times. At theconclusion of cleaning with this mode, the channel was rinsed withwater.

Sections were then cut at the beginning, middle and end of the channelfor examination by electron microscopy. Representative scanning electronmicrographs (SEMs) were acquired at 1000× and 5000× magnifications.Analysis of SEMs revealed that the DPDF flow regime is effective inachieving a high-level cleaning of similar quality as when air andcleaning liquid used in the RDF mode. This mode of cleaning allowsbetter distribution of surface flow entities with three phase contact onthe ceiling and bottom of the channel. It can be used alone or can becombined with other RDF mode to ensure achieving high treatment numberfor all parts of channel surface. High-speed images also indicated thatthe surface of the channel specially at both inlet and outlet portionsof the channel receive more effective treatment and more uniformcoverage with surface flow entities during cleaning with the DPDF. Theresults of this example support that periodic dewetting and drying ofchannel surface prevents adverse effects of liquid film formation on thesurface of the channel which has been found to impede the cleaning withsurface flow entities according the instant invention. The selection ofthe period of time for introducing the liquid, liquid flow rate, airpressure, air duration and surfactant type need to be selected toachieve effect effective cleaning. This cleaning mode is also effectiveduring rinsing and pre-cleaning of endoscopes since it provides moreuniform coverage of surface and minimizes incidents of low treatmentnumber in some parts of the channels specially the bottom section andboth inlet and outlet sections.

Example 20 Controlling Parameter for Endoscope Cleaning According to theCurrent Invention

Tables 14-16 provide the suggested liquid and gas flow rates atdifferent pressures for generating optimal RDF flow regimes for cleaningthe channels of most endoscopes currently available. The liquid cleaningused included 0.036% Surfynol-485W and 0.024% AO-455.

TABLE 14 Rivulet-droplet Flow Conditions: Endoscope - PENTAX ® EG-2901Set Pressure Flow 18 psig 24 psig 30 psig Rate of Channel ChannelChannel Channel Liquid Air Pres- Outlet Channel Air Pres- Outlet ChannelAir Pres- Outlet Channel Inside Cleaning Flow sure Veloc- Inlet Flowsure Veloc- Inlet Flow sure Veloc- Inlet Diameter Solution Rate Drop ityVelocity Rate Drop ity Velocity Rate Drop ity Velocity (cm) (ml/min)(scfm) (psid) (m/s) (m/s) (scfm) (psid) (m/s) (m/s) (scfm) (psid) (m/s)(m/s) Flow from Umbilical End to Distal End Air/Water 0.18 15 0.04 12.53.3 1.8 0.07 22.4 6.6 2.6 0.14 27.5 12.8 4.5 Suction 0.38 45 0.21 12.88.8 4.7 1.36 15.4 56.7 27.7 1.01 26.8 41.9 14.9 Flow from Control Handleto Distal End Air/Water 0.15 15 0.07 12.6 9.8 5.3 0.11 18.3 14.3 6.40.21 28.0 28.4 9.8 Suction 0.38 45 0.87 12.3 36.3 19.8 1.16 18.3 48.421.6 1.74 26.8 72.5 25.7 Biopsy 0.38 45 0.73 12.4 30.3 16.4 0.85 18.135.4 15.9 1.72 28.0 71.5 24.6 Flow from Control Handle to Umbilical EndAir/Water 0.18 15 1.37 12.6 127.5 68.7 1.61 18.4 149.6 66.5 1.91 24.0177.0 67.2 Suction 0.38 45 1.97 12.0 81.9 45.1 2.67 18.0 111.0 49.9 3.4224.6 142.2 53.2 Biopsy 0.38 45 1.95 12.3 81.2 44.3 2.47 18.1 103.0 46.13.19 25.0 132.8 49.2

TABLE 15 Rivulet-droplet Flow Conditions: Endoscope - PENTAX ®EC-3830TL) Set Pressure Flow 18 psig 24 psig 30 psig Rate of ChannelChannel Channel Channel Liquid Air Pres- Outlet Channel Air Pres- OutletChannel Air Pres- Outlet Channel Inside Cleaning Flow sure Veloc- InletFlow sure Veloc- Inlet Flow sure Veloc- Inlet Diameter Solution RateDrop ity Velocity Rate Drop ity Velocity Rate Drop ity Velocity (cm)(ml/min) (scfm) (psid) (m/s) (m/s) (scfm) (psid) (m/s) (m/s) (scfm)(psid) (m/s) (m/s) Flow from Umbilical End to Distal End Air/Water 0.1815 0.11 16.5 10.3 4.9 0.21 22.3 19.7 7.8 0.22 28.1 20.1 6.9 Suction 0.3845 1.83 16.0 76.1 36.4 2.19 22.0 91.1 36.5 2.56 27.6 106.5 37.0 Flowfrom Control Handle to Distal End Air/Water 0.15 15 0.15 16.4 19.7 9.30.29 22.3 38.9 15.5 0.44 28.0 58.2 20.0 Suction 0.38 45 2.60 15.3 54.126.5 3.04 22.0 63.2 25.3 3.76 27.4 78.3 27.3 Biopsy 0.38 45 2.81 15.258.5 28.8 3.76 21.6 78.3 31.7 5.47 26.6 113.9 40.5 Flow from ControlHandle to Umbilical End Air/Water 0.18 15 1.65 16.0 152.6 73.1 2.05 23.6190.4 73.1 2.44 25.8 226.1 82.1 Suction 0.38 45 2.62 15.2 109.2 53.73.26 21.9 135.7 54.2 3.94 27.5 163.8 57.1 Biopsy 0.38 45 2.29 15.2 95.346.8 2.84 23.0 118.1 46.0 4.08 27.5 169.7 59.1

TABLE 16 Rivulet-droplet Flow Conditions: Endoscope - OLYMPUS ®TJF-160VF Set Pressure Flow 30 psig 40 psig 60 psig Rate of ChannelChannel Channel Channel Liquid Air Pres- Outlet Channel Air Pres- OutletChannel Air Pres- Outlet Channel Inside Cleaning Flow sure Veloc- InletFlow sure Veloc- Inlet Flow sure Veloc- Inlet Diameter Solution RateDrop ity Velocity Rate Drop ity Velocity Rate Drop ity Velocity (cm)(ml/min) (scfm) (psid) (m/s) (m/s) (scfm) (psid) (m/s) (m/s) (scfm)(psid) (m/s) (m/s) Flow from Control Handle to Distal End Elevator 0.0853.8 0.050 26.0 82.8 29.9 Elevator 0.085 7.6 0.010 26.0 16.6 6.0 0.03536.0 58.0 16.8 0.078 56.0 129.2 26.7 Elevator 0.085 11.5 0.001 26.0 1.70.6 0.014 36.0 22.4 6.5 0.050 56.0 82.8 17.2

Example 21 Eductor System and Basin Design with Eductor on Two Sides ofBasin

To investigate the effectiveness of the eductor system design, anexperiment was performed using a simple plastic container of dimensions24 inch length by 24 inch width by 12 inch depth to test the efficiencyof eductors having different nozzle sizes (0.125 inch to 0.375 inch).The eductors were mounted on two sides of the basin as illustrated inFIG. 22 b. The preliminary eductor system was driven by a ⅓ Horsepowerpump 840 and was controlled with two manual ball valves in a circulationsystem. These initial test results indicated that eductors with a 0.25″nozzle diameter are the most effective size for cleaning the exteriorsurfaces of endoscopes. Each eductor delivered up to 3.5 gallons perminute (gpm) of cleaning solution from the driven pump 840 and pulled upto 12.7 gpm additional flow from the surrounding liquid to create atotal flow rate of approximately 16.2 gpm that impinged onto theendoscope surface.

Example 22 Eductor System and Basin Design with Eductors in Corners ofBasin

An experimental basin was designed and constructed to test the flowpattern and fluid dynamics generated by multiple eductors placed incorners of the basin, with an objective to closely simulate the case forcleaning two endoscopes. This is illustrated in FIG. 22 c. The basin wasconstructed from acrylic plates glued together and measured was 30 inchwide×28 inch deep×6 inch high. Internal slopes were added to the bottomplates to reduce the total volume needed for both cleaning anddisinfection while still achieving full immersion of the endoscopes. Twoeductors were installed at each corner of the basin and each eductor wasconnected with a manual ball valve for testing the effect of differentcombinations on the flow pattern created in the basin. The eductorsystem was connected with a ⅓ Horsepower pump to circulate the cleaningliquid at a source pressure of approximately 15˜20 psig. In this design,when the eductors were placed about 0.5 inch beneath the cleaningsolution level, we observed very strong flow patterns that covered mostexterior surfaces of endoscopes, especially when three or four eductorswere operated simultaneously, one at each corner. The cleaning liquidlevel in this experiment was about 3 inch to 4 inch from the bottom ofthe basin. With this setting, a strong scrubbing and agitation was foundto be generated in the spaces near the bottom of the basin, whereas theearlier top spray design could not reach endoscope surfaces facing thebasin. A favorable arrangement for cleaning endoscopes was found whentwo eductors were installed at each front corner (total of 4 in thefront of the basin) and one at each back corner of the basin (total of 2at the bottom of the basin. It is also possible to have two eductors ateach corner of the basin.

Example 23 Eductor System and Basin Design for Entrainment of Air inFluid Moved by Eductors

We have also discovered that if part of the entrained liquid pulled intothe eductor 800 comprises air such as in the form of air bubbles, thenthe impingement and agitation forces impacting the exterior surfaces ofendoscopes can further enhance the cleaning process. This can beachieved, for example, by placing the eductor 800 close to the level ofthe surface of the liquid in the basin 850, so that some air can bepulled into the eductor 800 in addition to liquid. This is illustratedin FIG. 22 d.

Another way of accomplishing this is with a design as shown in FIG. 22e. This design, which resembles what was shown in FIG. 13 d, furtherincludes an air intake tube 862 suitable to provide air from the headspace of the basin apparatus to the suction region 822 or mixing region824 of the eductor 800. The fluid leaving the eductor 800 may therebyinclude air bubbles as well as liquid.

Example 24 RDF Cleaning Using an Alcohol-Water Solution

It was attempted to perform cleaning using rivulet droplet flow using aliquid which was a solution of alcohol and water. In general, it is easyto adjust the composition of an alcohol-water solution to achieve adesired surface tension, and of course, alcohols are simplereadily-available compounds. Experiments were conducted using ethanoland also using methanol, n-butanol and t-butanol. The surface tension ofthese solutions was adjusted to a value of about 40 dynes/cm, which withother surfactant compositions was found to be a desirable value. None ofthese alcohol-water solutions produced good cleaning, apparently becauseof liquid film remaining and the surface not becoming completely dry.

Example 25 RDF Cleaning Using a Higher-Viscosity Liquid

An experiment was performed to investigate cleaning using a liquidhaving a viscosity larger than the viscosity of water. The liquid was asolution of water containing 0.05% by weight of polyvinyl pyrrolidone (athickener). It was found that such a liquid resulted in formation offilms which prevented achieving a dry surface and led to a significantdecrease in the formation of desired surface flow entities. So, this wasundesirable for cleaning, even if the surface tension of the liquid waswithin the desirable range. It may be considered that it is desirablefor the liquid to have approximately the viscosity of pure water.

In many applications the passageways have a uniform circular crosssection (circular), in which case the “average” diameter is the actualphysical internal diameter of the channel. However, the described methodcan also be used for passageways that are neither circular in crosssection nor of uniform diameter, i.e., the passageways may have kinks,restrictions, bends, etc.

It has mostly been described herein that the passageway being cleaned isin a horizontal orientation. However, in general any orientation ispossible, including combinations of orientations. For example, thepassageway could be vertical, or diagonal (with flow either upward ordownward), or any combination of these or any other orientations. Forexample, bronchoscopes could be cleaned in a vertical orientation.

It is further possible to use the described rivulet droplet flow inprocesses that are not the actual step which is described herein as thecleaning step. For example, rinsing may be performed at a certain stageof an overall cleaning cycle, and rinsing could be performed usingrivulet droplet flow either partly or completely. Similarly, there is astep labeled pre-cleaning which is oriented toward removing macroscopiccontaminants from channels. This step also could be performed usingrivulet droplet flow either partly or completely. It is possible thatsome cleaning could be accomplished during these steps even if that isnot the primary purpose of these steps. In general, it is possible thatcleaning could be accomplished during steps other than the main cleaningstep. A pre-cleaning step could involve use of a surfactant composition,which may or may not be the same surfactant composition used in anyother step of the process. Use of rivulet droplet flow in any of thesesteps could be either rivulet droplet flow with steady-state suppliedfluid flows, or rivulet flow with unsteady (time-varying) supplied flowof either liquid or gas or both. For example, it is possible that ifrivulet droplet flow is used during a step that involves flowing alcoholor alcohol-water through the passageway (a rinsing or drying step), itmay be possible to use less alcohol and still accomplish the desiredobjective.

It is furthermore possible to clean passageways whose cross-sectionalshape is other than circular or even annular as described. For example,passageway cross-sectional shapes capable of being cleaned by thedescribed method and apparatus include elliptical and rectangular, andalso include other combinations of co-existing shapes beyond thedescribed circular wire in a circular channel. It may be possible toclean something that does not have the geometry of a passageway, usingthe described method or apparatus, by enclosing it in a passageway or byplacing something adjacent to the article so that together the articleand the extra thing form a passageway.

Although the cleaning methods have been disclosed for passageways havingan inside diameter of the order of 6 mm or less, the usefulness of themethod is not limited to such relatively small passageways. It isbelieved that the method could similarly be applied to passagewayshaving inside diameters at least of the order of centimeters or inches.It is believed that for such extrapolation, a useful scaling parametermay be the perimeter-normalized liquid flowrate as discussed elsewhereherein. It is also possible that the described method or apparatus couldbe used for passageways smaller in diameter than those investigated,such as for cleaning microfluidic articles.

It is still further possible that the described method or apparatuscould be used for still other industrial or household cleaning. Liquidentities could be moved by moving gas even in the absence of a definedpassageway, and operations could be sequenced so as to achieve repeateddryout and re-wetting as described elsewhere herein.

It can again be mentioned that the presence of a dry surfaceencountering a moving liquid entity is believed to contribute tocleaning, and that apparatus and methods of embodiments of the presentinvention can be arranged so as to create or ensure that dry surfacebetween encounters with moving liquid entities. The dryness can beachieved by evaporation of liquid into the flowing gas, or byhydrophobicity of the surface, or by any combination thereof. In theplug mode of operation, gas flow can be continued between liquid plugsfor a time duration sufficient to achieve de-wetting such as byevaporation. It can be appreciated that, in contrast, much of classicaltwo-phase liquid-gas flow never achieves dryness of the wall in betweenencounters with liquid entities.

Although much of the discussion herein has been about cleaningpassageways that have a horizontal orientation, the applicability ofthis method and apparatus is not limited thereto. It is possible thatthe method and apparatus described herein could be used to cleanpassageways that have a horizontal orientation, a vertical orientation,a diagonal orientation, or any combination of any of these orientations.Different portions of the passageway could have different orientations.As described, the driving force for the motion of rivulets and otherliquid entities has been motion of gas. However, it is possible that thedriving force could be gravity, or a combination of gravity and gasflow.

It is believed that performing the cleaning process a generally somewhatelevated temperature enhances the effectiveness of the cleaning. It isto this end that pre-heating of the liquid and pre-heating of the gasare provided for, as described elsewhere herein.

Most of the experimental data reported herein has been taken usingpassageways made of polytetrafluoroethylene (Teflon®), which is arelatively hydrophobic material. However, the apparatus and methodscould also be used for cleaning passageways made of other materials,possibly with adjustment of the composition of the liquid.

It is possible to record of parameters experienced during the cleaningcycle. Such information may be stored in any form of computer memory orwritten onto a storage device. The apparatus may comprise User Interfacefeatures designed with the device which may include a display, akeyboard, a barcode reader and data transition connectors that willallow the operator to select and set process parameters and documentcleaning results for reprocessing different types of endoscopes.

As described, embodiments of the invention can be used in anyorientation of passageway, such as horizontal or vertical or slopingorientations or combinations thereof. The achievement of a dry orsubstantially dry passageway interior surface, prior to being swept by aliquid entity, can be achieved by evaporation or by the inherenthydrophobicity of the surface, or through the use of a surfactantadditive in the liquid which increases the hydrophobocity of thesurface, or by any combination thereof. It can be appreciated that aflow of liquid which enters a passageway as a plug of liquid might notmaintain exactly that geometry during an entire passage through thepassageway; however, that can be acceptable because a plug which isdeveloping some irregularities during its passage through the passagewaycan still sweep the internal surface of the passageway so as to removecontaminants, and if the plug breaks up into other liquid entities,there may be even more sweeping than with an intact plug. Plug flow canrefer to Discontinuous Plug Flow (DPF) and Discontinuous Plug DropletFlow (DPDF), as described elsewhere herein. In plug flow, which may beachieved by supplying liquid for a period of time followed by supplyinggas for a period of time, it is possible that the plug may beaccelerated to a fairly large velocity. i.e., larger than the velocityof a sliding liquid entity, while still remaining within an overallmaximum pressure of gas supplied to the passageway inlet. For example,if the plug only occupies a small fraction such as 10% of the overalllength of the passageway, the plug can reach a velocity significantlylarger than the velocity of a liquid filling the entire length of thepassageway, for the same driving pressure difference, as describedelsewhere herein. This can produce correspondingly larger viscous shearat the walls of the passageway. The same is true if there are a numberof such plugs having a combined total length that is a small fractionsuch as 10% of the overall length of the passageway. A flow regime canbe rivulet droplet flow, plug flow, or meandering rivulet flow, or stillother flow regime. It is believed that use of rivulet droplet flow orplug flow or other flow regimes involving liquid and gas during rinsingcan produce rinsing just as can be provided by a flow of water only, andit is further believed that some additional cleaning occurs therebyduring the rinsing step. It may be viewed that the entire treatmentnumber during the cleaning/reprocessing cycle is the sum of treatmentnumber components arising from the application of the above flow regimes(RDF, DPF, DPDF) during pre-cleaning, cleaning, rinsing after cleaningand rinsing after disinfection. It is also believed that rinsing withwater only according to the above flow regimes may be considered as aportion of the entire cleaning cycle.

Unsteady flow can be provided in a manner which either could be periodic(repeating in a defined pattern) or could be non-periodic, i.e.,time-varying in a more irregular manner. A periodic pattern could, forexample, comprise at least 10 repeated periods. In general, for variouspurposes, any timewise pattern of liquid supply (on/off or pulsatile ora more gradual variation) could be combined with any timewise pattern ofgas supply (on/off or pulsatile or a more gradual variation). If twopassageways or two endoscopes are being cleaned simultaneously, steps inone passageway or endoscope can in general be done in any timewiserelationship with steps in the other passageway or endoscope. Mass fluxis mass flow per unit cross-sectional flow area per unit time. In theuse of eductors for cleaning external surfaces of an endoscope, it ispossible to have any time sequence of operating specific eductors. Thiscan provide different flow patterns of liquid in the basin at differenttimes.

An embodiment of the present invention is related to special ability ofthe rivulet droplet flow and associated three phase contact line andmenisci to interact with the organic soils inside the endoscoperesulting in their effective removal from the channels. These specialabilities may be due to interaction of the organic soil with the threephase contact line and menisci generated during RDF, PDF and DPDF. Thehigher plug velocities generated in the case of a short plug (comparedto channel length) by the gas flow and its associated three phasecontact line and menisci were found to be specially effective indislodging and removing bulky pieces of soil (for example, feces fromendoscope channels) compared to liquid flow cleaning.

The apparatus may comprise a tray or similar apparatus for holding anendoscope or other luminal medical device in a desired orientation.

It is found that cleaning with the methods and apparatus describedherein may actually provide better results than manual cleaning ofendoscopes such as with a brush, and likely more consistent results.

All cited references are incorporated by reference herein in theirentirety.

Although embodiments and examples have been given, modifications arepossible, and it is desired that the scope be limited only by the scopeof the attached claims.

We claim:
 1. A method of cleaning a passageway, comprising: supplying aflow of a gas to the passageway along an interior surface of thepassageway; and supplying a flow of a liquid to the passageway along theinterior surface of the passageway forming sliding liquid entities alongthe interior surface of the passageway, wherein said sliding liquidentities provide a moving three-phase interface on the interior surfaceof the passageway having an advancing contact angle on at least aportion of the interior surface of the passageway greater than about 50degrees and having a receding contact angle greater than 0 degree sothat a portion of the interior surface of the passageway is wetted bythe liquid and an adjacent portion of the interior surface of thepassageway is dry or nearly dry.
 2. The method of claim 1, wherein thegas is supplied to the passageway at a substantially constant flow ratewhile the liquid is supplied to the passageway in a pulsatile manner. 3.The method of claim 2, wherein said pulsatile manner comprisesalternating periods of greater liquid flowrate and lesser liquidflowrate, or comprises alternating periods of a finite liquid flowrateand periods of zero liquid flowrate.
 4. The method of claim 3, whereinthe periods of zero liquid flowrate are of a duration such that internalsurfaces of the passageway are essentially completely dry before a nextone of the periods of the finite liquid flowrate.
 5. The method of claim1, wherein said gas and said liquid are delivered to more than one ofthe passageways simultaneously.
 6. The method of claim 1, wherein thepassageway is part of an endoscope.
 7. The method of claim 1, whereinthe passageway is part of medical luminal instrument.